Organic Light Emitting Display Device Comprising Multi-Type Thin Film Transistor and Method of Manufacturing the Same

ABSTRACT

An organic light emitting display device includes a driving TFT on the substrate, a switching TFT on the substrate, and an organic light emitting diode. The driving TFT includes a first active layer formed of poly-Si, and at least a first part of an interlayer insulation layer on the first active layer. The interlayer insulation layer is formed of a first material including hydrogen. The switching TFT includes a second active layer, at least a second part of the interlayer insulation layer between the first active layer and the second active layer, and at least a part of a gate insulation layer between the second part of the interlayer insulation layer and the second active layer. The gate insulation layer is formed from a second material different from the first material and blocking diffusion of hydrogen from the interlayer insulation layer to the second active layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/624,559 filed on Jun. 15, 2017, which claims thepriority of Republic of Korea Patent Application No. 10-2016-0085783filed on Jul. 6, 2016, Republic of Korea Patent Application No.10-2016-0143777 filed on Oct. 31, 2016 and Republic of Korea PatentApplication No. 10-2016-0143773 filed on Oct. 31, 2016, in the KoreanIntellectual Property Office, the disclosure of each of which isincorporated herein by reference.

BACKGROUND Field

The present disclosure relates to an organic light emitting displaydevice including a multi-type thin film transistor and a method ofmanufacturing the organic light emitting display device and moreparticularly, to an organic light emitting display device in whichdifferent types of thin film transistors are disposed on a singlesubstrate and a method of manufacturing the organic light emittingdisplay device.

Description of the Related Art

Recently, as the world reached a full-scale information age, the fieldof display for visually displaying electrical information signals hasgrown rapidly. In response thereto, various flat display devices withexcellent performance in terms of thinning, weight lightening, and lowpower consumption have been developed and have rapidly replaced cathoderay tube (CRT) displays that have been used in the art.

Specific examples of the flat display devices include a liquid crystaldisplay (LCD) device, an organic light emitting display (OLED) device,an electro phoretic display (EPD) device, a plasma display panel (PDP)device, and an electro-wetting display (EWD) device, and the like.Particularly, the OLED device, which is a next-generation display devicewith self-emitting characteristics, has excellent characteristics interms of viewing angle, contrast, response speed, power consumption,etc., as compared with the LCD device.

The OLED device includes a display area where an organic light emittingelement for displaying an image and a pixel circuit for driving theorganic light emitting element are disposed. Also, the OLED deviceincludes a non-display area which is adjacent to the display area and inwhich a driving circuit is disposed. Particularly, a plurality of thinfilm transistors is positioned in the pixel circuit and the drivingcircuit so as to drive organic light emitting elements in a plurality ofpixels.

The thin film transistors can be classified by the material of an activelayer. Particularly, a low temperature poly-silicon (LTPS) thin filmtransistor and an oxide semiconductor thin film transistor are commonlyused. However, currently, in an OLED device, either the LTPS thin filmtransistor or the oxide semiconductor thin film transistor is used on asingle substrate as a thin film transistor constituting a pixel circuitand a driving circuit. However, if any one of the LTPS thin filmtransistor or the oxide semiconductor thin film transistor constitutesthe pixel circuit and the driving circuit, there are various problems.Accordingly, there has been a need to apply different types of thin filmtransistors to a single OLED device.

SUMMARY

The inventors of the present disclosure recognized the above-describedneed and researched a technology of applying different types of thinfilm transistors to a single substrate. Then, the inventors invented anorganic light emitting display device to which an LTPS thin filmtransistor and an oxide semiconductor thin film transistor are applied.However, inventors of the present disclosure recognized various problemscaused by application of the LTPS thin film transistor and an oxidesemiconductor thin film transistor to the single substrate.

Firstly, hydrogen contained in an interlayer insulation layer of theLTPS thin film transistor and used for a hydrogenation process of anactive layer of the LTPS thin film transistor may be diffused into anactive layer of the oxide semiconductor thin film transistor. Thus, athreshold voltage (Vth) of the oxide semiconductor thin film transistormay be changed.

Further, inorganic films of an encapsulation unit used in an OLED deviceneed to be formed on an organic light emitting element and thus areformed by a low-temperature process. However, the inorganic films formedby a low-temperature process contain a relatively large amount ofhydrogen. Such hydrogen is diffused into the active layer of the oxidesemiconductor thin film transistor, and, thus, there is a problem thatthe threshold voltage (Vth) of the oxide semiconductor thin filmtransistor may be changed.

Also, a large amount of hydrogen may be diffused into the active layerof the oxide semiconductor thin film transistor depending on the timingof an activation process and a hydrogenation process of the active layerof the LTPS thin film transistor in a manufacturing process of theorganic light emitting display device.

Accordingly, an object to be achieved by the present disclosure is toprovide a new structure of an organic light emitting display device forsolving the above-described problems and a new method of manufacturingan organic light emitting display device.

Specifically, the object to be achieved by the present disclosure is toprovide an organic light emitting display device and a method ofmanufacturing the organic light emitting display device. In the organiclight emitting display device, a lamination structure and materials ofan interlayer insulation layer of an LTPS thin film transistor and agate insulation layer and a passivation layer of an oxide semiconductorthin film transistor are variously designed. Thus, the organic lightemitting display device is capable of reducing diffusion of hydrogenfrom the interlayer insulation layer or an encapsulation unit of theLTPS thin film transistor into an active layer of the oxidesemiconductor thin film transistor.

Another object to be achieved by the present disclosure is to provide amethod of manufacturing an organic light emitting display device bywhich diffusion of hydrogen into an active layer of an oxidesemiconductor thin film transistor can be reduced while an activationprocess and a hydrogenation process are performed to an LTPS thin filmtransistor.

The objects of the present disclosure are not limited to theaforementioned objects, and other objects, which are not mentionedabove, will be apparent to a person having ordinary skill in the artfrom the following description.

According to an aspect of the present disclosure, there is provided anorganic light emitting display device including a multi-type thin filmtransistor. The organic light emitting display device includes asubstrate defined into a display area and a non-display area positionedon one side of the display area, an LTPS thin film transistor and anoxide semiconductor thin film transistor disposed on the display area, alower insulation layer and an upper insulation layer respectivelypositioned under and on an active layer of the oxide semiconductor thinfilm transistor, and an organic light emitting element positioned on theLTPS thin film transistor and the oxide semiconductor thin filmtransistor. The lower insulation layer or the upper insulation layer isformed as a multi-layer structure having at least one difference in filmdensity or hydrogen content to minimize exposure of the active layer tohydrogen.

According to another feature of the present disclosure, the lowerinsulation layer includes a first insulation layer and a secondinsulation layer. The second insulation layer is disposed on the firstinsulation layer so as to be in contact with the active layer. The firstinsulation layer and the second insulation layer may be formed ofdifferent materials. The second insulation layer may have a higherhydrogen content than the first insulation layer.

According to yet another feature of the present disclosure, the lowerinsulation layer includes a first insulation layer and a secondinsulation layer. The second insulation layer is disposed on the firstinsulation layer so as to be adjacent to the active layer. The firstinsulation layer and the second insulation layer may be formed of thesame material. The second insulation layer may have a higher hydrogencontent than the first insulation layer.

According to still another feature of the present disclosure, the upperinsulation layer includes a third insulation layer and a fourthinsulation layer. The third insulation layer is in contact with theactive layer. The fourth insulation layer is disposed on the thirdinsulation layer. The third insulation layer may have a higher filmdensity than the fourth insulation layer.

According to an aspect of the present disclosure, there is provided amethod of manufacturing an organic light emitting display deviceincluding a multi-type thin film transistor. The method of manufacturingan organic light emitting display device includes forming a first activelayer of an LTPS thin film transistor on a substrate, forming a gateelectrode of the LTPS thin film transistor on the first active layer,forming an insulation layer on the gate electrode, forming a secondactive layer of an oxide semiconductor thin film transistor on theinsulation layer, forming a first source electrode and a first drainelectrode of the oxide semiconductor thin film transistor and a secondsource electrode and a second drain electrode of the LTPS thin filmtransistor on the insulation layer, and forming a passivation layercovering the first source electrode, the second source electrode, thefirst drain electrode, and the second drain electrode. The first sourceelectrode, the second source electrode, the first drain electrode, andthe second drain electrode are formed of the same material at the sameprocess. The insulation layer or the passivation layer is formed as amulti-layer structure, and each layer of the passivation layer has adifferent property.

According to still another feature of the present disclosure, theforming of an insulation layer includes forming a first insulation layeron the gate electrode and forming a second insulation layer on the firstinsulation layer. Each of the forming of a first insulation layer andthe forming of a second insulation layer includes injecting an injectionsource into a chamber. The injection source may include a silane (SiH₄)gas.

According to still another feature of the present disclosure, in theforming of a first insulation layer and the forming of a secondinsulation layer, the first insulation layer and the second insulationlayer are formed of the same material. The second insulation layer mayhave a higher film density than the first insulation layer toeffectively block hydrogen.

According to still another feature of the present disclosure, the amountof the silane gas injected in the forming of a second insulation layermay be smaller than the amount of the silane gas injected in the formingof a first insulation layer.

Embodiments also relate to an organic light emitting display device,including a substrate and a pixel on the substrate. The pixel includes adriving thin film transistor (TFT) on the substrate, a switching TFT onthe substrate, and an organic light emitting diode (OLED). The drivingTFT includes a first active layer formed of poly-Si, and at least afirst part of an interlayer insulation layer on the first active layer.The interlayer insulation layer is formed of a first material includinghydrogen. The switching TFT includes a second active layer, at least asecond part of the interlayer insulation layer between the first activelayer and the second active layer, and at least a part of a gateinsulation layer between the second part of the interlayer insulationlayer and the second active layer. The gate insulation layer is formedfrom a second material different from the first material and blockingdiffusion of hydrogen from the interlayer insulation layer to the secondactive layer. The OLED is electrically connected to the driving TFT.

Embodiments also relate to an organic light emitting display device,including a substrate and a pixel on the substrate. The pixel includes afirst active layer of a first thin film transistor (TFT) on thesubstrate. The first active layer is formed of oxide semiconductor. Thepixel also includes a second active layer of a second TFT on thesubstrate. The second active layer is formed of poly-Si. The pixel alsoincludes a first insulation layer between the first active layer and thesecond active layer. The first insulation layer is formed of a firstmaterial including hydrogen. The pixel also includes a second insulationlayer between the first insulation layer and the second first activelayer. The second insulation layer is formed of a second materialdifferent from the first material and blocking diffusion of hydrogenfrom the first insulation layer to the second first active layer. TheOLED is electrically connected to the second TFT.

Details of other exemplary embodiments will be included in the detaileddescription of the invention and the accompanying drawings.

According to the present disclosure, it is possible to provide anorganic light emitting display device having a new structure capable ofsolving various problems occurring when a multi-type thin filmtransistor is applied to a single substrate and a method ofmanufacturing the new organic light emitting display device.

Specifically, according to the present disclosure, diffusion of hydrogencontained in various insulation layers within the organic light emittingdisplay device into an active layer of an oxide semiconductor thin filmtransistor can be reduced. Thus, the reliability of the oxidesemiconductor thin film transistor can be improved.

According to the present disclosure, an activation process and ahydrogenation process of an LTPS thin film transistor are optimized.Thus, the reliability of the oxide semiconductor thin film transistorcan be improved.

The effects of the present disclosure are not limited to theaforementioned effects, and various other effects are included in thepresent specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a cross-sectional view of an organic light emitting displaydevice including a multi-type thin film transistor according to anembodiment of the present disclosure.

FIG. 2A and FIG. 2B are cross-sectional views provided to explain aneffect of hydrogen diffusion from an interlayer insulation layer on anoxide semiconductor thin film transistor in an organic light emittingdisplay device according to a Comparative Example.

FIG. 2C is a cross-sectional view provided to explain an effect ofhydrogen diffusion from an interlayer insulation layer on an oxidesemiconductor thin film transistor in an organic light emitting displaydevice including a multi-type thin film transistor according to anembodiment of the present disclosure.

FIG. 3A is a cross-sectional view provided to explain an effect ofhydrogen diffusion from an encapsulation unit on an oxide semiconductorthin film transistor in an organic light emitting display deviceincluding a multi-type thin film transistor according to an embodimentof the present disclosure.

FIG. 3B is an enlarged view of an area A of FIG. 3A.

FIG. 4A is a cross-sectional view of an organic light emitting displaydevice including a multi-type thin film transistor according to anotherembodiment of the present disclosure.

FIG. 4B is an enlarged view of an area A of FIG. 4A.

FIG. 5 is a cross-sectional view of an organic light emitting displaydevice including a multi-type thin film transistor according to yetanother embodiment of the present disclosure.

FIG. 6A is a cross-sectional view provided to explain an effect of asubstrate and a buffer layer in an organic light emitting display deviceincluding a multi-type thin film transistor according to an embodimentof the present disclosure.

FIG. 6B and FIG. 6C are cross-sectional views of organic light emittingdisplay devices each including a multi-type thin film transistoraccording to various embodiments of the present disclosure.

FIG. 7 is a schematic flowchart of a method of manufacturing an organiclight emitting display device including a multi-type thin filmtransistor according to an embodiment of the present disclosure.

FIG. 8A through FIG. 8I are process cross-sectional views of a method ofmanufacturing an organic light emitting display device including amulti-type thin film transistor according to an embodiment of thepresent disclosure.

FIG. 9 is a cross-sectional view of an organic light emitting displaydevice including a multi-type thin film transistor according to stillanother embodiment of the present disclosure.

FIG. 10A is a schematic flowchart of an activation process and ahydrogenation process of an LTPS thin film transistor in a method ofmanufacturing an organic light emitting display device including amulti-type thin film transistor according to a Comparative Example.

FIG. 10B and FIG. 10C are schematic flowcharts of an activation processand a hydrogenation process of an LTPS thin film transistor in a methodof manufacturing an organic light emitting display device including amulti-type thin film transistor according to an embodiment and anotherembodiment of the present disclosure.

FIG. 11 is a table of Vth MAP and Vth variation caused by an activationprocess and a hydrogenation process of an LTPS thin film transistor in amethod of manufacturing an organic light emitting display deviceincluding a multi-type thin film transistor according to an embodimentof the present disclosure and the Comparative Example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Advantages and features of the present disclosure, and methods foraccomplishing the same will be more clearly understood from exemplaryembodiments described below with reference to the accompanying drawings.However, the present disclosure is not limited to the followingexemplary embodiments but may be implemented in various different forms.The exemplary embodiments are provided only to complete disclosure ofthe present disclosure and to fully provide a person having ordinaryskill in the art to which the present disclosure pertains with thecategory of the disclosure, and the present disclosure will be definedby the appended claims.

The shapes, sizes, ratios, angles, numbers, and the like illustrated inthe accompanying drawings for describing the exemplary embodiments ofthe present disclosure are merely examples, and the present disclosureis not limited thereto. Like reference numerals generally denote likeelements throughout the present specification. Further, in the followingdescription, a detailed explanation of known related technologies may beomitted to avoid unnecessarily obscuring the subject matter of thepresent disclosure. The terms such as “including,” “having,” and“consist of” used herein are generally intended to allow othercomponents to be added unless the terms are used with the term “only”.Any references to singular may include plural unless expressly statedotherwise.

Components are interpreted to include an ordinary error range even ifnot expressly stated.

When the position relation between two parts is described using theterms such as “on”, “above”, “below”, and “next”, one or more parts maybe positioned between the two parts unless the terms are used with theterm “immediately” or “directly”.

When an element or layer is referred to as being “on” another element orlayer, it may be directly on the other element or layer, or interveningelements or layers may be present.

Although the terms “first”, “second”, and the like are used fordescribing various components, these components are not confined bythese terms. These terms are merely used for distinguishing onecomponent from the other components. Therefore, a first component to bementioned below may be a second component in a technical concept of thepresent disclosure.

Throughout the whole specification, the same reference numerals denotethe same elements.

Since the size and thickness of each component illustrated in thedrawings are represented for convenience in explanation, the presentdisclosure is not necessarily limited to the illustrated size andthickness of each component.

The features of various embodiments of the present disclosure can bepartially or entirely bonded to or combined with each other and can beinterlocked and operated in technically various ways as can be fullyunderstood by a person having ordinary skill in the art, and theembodiments can be carried out independently of or in association witheach other.

Hereinafter, various embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings.

In organic light emitting display devices each including a multi-typethin film transistor according to various embodiments of the presentdisclosure, at least two types of thin film transistors are formed onthe same substrate. A multi-type thin film transistor refers todifferent types of thin film transistors formed on a single substrate.Herein, a thin film transistor including an active layer formed of apoly-silicon material and a thin film transistor including an activelayer formed of a metal oxide are used as at least two types of thinfilm transistors.

In the organic light emitting display devices each including amulti-type thin film transistor according to various exemplaryembodiments of the present disclosure, an LTPS thin film transistorusing low temperature poly-silicon is used as the thin film transistorincluding an active layer formed of a poly-silicon material. Thepoly-silicon material has high mobility (100 cm²/Vs or more), low energypower consumption and excellent reliability. Thus, the LTPS thin filmtransistor can be applied to a gate driver and/or multiplexer (MUX) foruse in a driving element for driving thin film transistors for displaydevice. Preferably, the LTPS thin film transistor may be applied todriving thin film transistors within pixels of an organic light emittingdisplay device.

Also, in the organic light emitting display devices each including amulti-type thin film transistor according to various exemplaryembodiments of the present disclosure, an oxide semiconductor thin filmtransistor including an active layer formed of an oxide semiconductormaterial is used. The oxide semiconductor material has a greater bandgap than a silicon material, so that an electron cannot cross the bandgap in an off state and an off-current is low. Therefore, the oxidesemiconductor thin film transistor is suitable for switching thin filmtransistors which remain on for a short time and off for a long time.Also, since the off-current is low, the size of an auxiliary capacitancecan be reduced. Therefore, the oxide semiconductor thin film transistoris suitable for high-resolution display elements.

In the organic light emitting display devices each including amulti-type thin film transistor according to various embodiments of thepresent disclosure, the LTPS thin film transistor and the oxidesemiconductor thin film transistor having different properties aredisposed on the same substrate. Thus, it is possible to provide optimumfunctionality.

FIG. 1 is a cross-sectional view of an organic light emitting displaydevice including a multi-type thin film transistor according to anembodiment of the present disclosure. FIG. 1 is a cross-sectional viewof a partial area of a single pixel in an organic light emitting displaydevice 100, and illustrates an LTPS thin film transistor 130, an oxidesemiconductor thin film transistor 140, and a storage capacitor 120.

Referring to FIG. 1, the organic light emitting display device 100includes a substrate 110, a buffer layer 111, the oxide semiconductorthin film transistor 140, the LTPS thin film transistor 130, the storagecapacitor 120, a gate insulation layer 112 of the LTPS thin filmtransistor 130, an interlayer insulation layer 150, a gate insulationlayer 160 of the oxide semiconductor thin film transistor 140, apassivation layer 170, an overcoating layer 113, an organic lightemitting element 180, and an encapsulation unit 190.

The LTPS thin film transistor 130 illustrated in FIG. 1 is a top gate orcoplanar thin film transistor in which a gate electrode 134 is disposedon an active layer 131. Further, the oxide semiconductor thin filmtransistor 140 is a back channel etch (BCE) thin film transistor inwhich a gate electrode 144 is separated from a source electrode 142 anda drain electrode 143 by an active layer 141 disposed therebetween.However, the present disclosure is not limited to the above-describedstructure.

Hereinafter, each of the components of the organic light emittingdisplay device 100 will be described in detail.

The substrate 110 supports various components of the organic lightemitting display device 100. The substrate 110 may be formed of glass ora plastic material having flexibility. For example, the substrate 110may be formed of polyimide (PI). If the substrate 110 is formed ofpolyimide (PI), a manufacturing process of an organic light emittingdisplay device may be performed in a state where a supporting substrateformed of solid glass is disposed under the substrate 110. In this case,the supporting substrate is removed during the manufacturing process.Further, after the supporting substrate is removed, a back plate forsupporting the substrate 110 may be disposed under the substrate 110.

If the substrate 110 is formed of a plastic material, moisture orhydrogen permeating into the organic light emitting display device 100from under the substrate 110 can be suppressed more reliably. In orderto shield an electrical effect from the outside more reliably, thesubstrate 110 may be formed as a multi-layer structure. For example, thesubstrate 110 may be formed as a three-layer structure including aplastic layer/an inorganic film/a plastic layer. In this case, theinorganic film may be formed of silicon nitride (SiNx) to block moistureor hydrogen more reliably, or may be formed of a metal material toshield an electrical effect more reliably. Further, a constant voltagemay be applied to an inorganic film formed of a metal material, so thatelectrical shielding can be achieved more completely.

Referring to FIG. 1, the buffer layer 111 is formed on the entiresurface of the substrate 110. The buffer layer 111 may be formed as asingle layer of silicon nitride (SiNx) or silicon oxide (SiOx) or amulti-layer of silicon nitride (SiNx) and silicon oxide (SiOx). Thebuffer layer 111 improves an adhesive force between layers formed on thebuffer layer 111 and the substrate 110 and blocks alkali elementsdischarged from the substrate 110. However, the buffer layer 111 is notan essential component, but may be omitted depending on the kind andmaterial of the substrate 110 and a structure or type of the thin filmtransistor.

Referring to FIG. 1, the LTPS thin film transistor 130 is disposed onthe buffer layer 111. The LTPS thin film transistor 130 includes theactive layer 131 formed of poly-silicon, the gate electrode 134 formedof a conductive metal material, a source electrode 132, and a drainelectrode 133.

The active layer 131 of the LTPS thin film transistor 130 is disposed onthe buffer layer 111. The active layer of the LTPS thin film transistor130 includes a channel area CA where a channel is formed when the LTPSthin film transistor 130 is driven and a source area SA and a drain areaDA on both sides of the channel area CA. The channel area CA, the sourcearea SA, and the drain area DA are defined by ion doping (impuritydoping).

The active layer 131 of the LTPS thin film transistor 130 containspoly-silicon. An amorphous-silicon (a-Si) material is deposited on thebuffer layer 111 and a dehydrogenation process and a crystallizationprocess are performed thereto, so that poly-silicon is formed. Theactive layer 131 is formed by patterning the poly-silicon. Further,after the interlayer insulation layer 150 of the LTPS thin filmtransistor 130 to be described later is formed, an activation processand a hydrogenation process are further performed, so that the activelayer 131 is completed. A manufacturing process of the active layer 131of the LTPS thin film transistor 130 will be described later.

Referring to FIG. 1, the gate insulation layer 112 of the LTPS thin filmtransistor 130 is disposed on the active layer 131 and the buffer layer111 of the LTPS thin film transistor 130. The gate insulation layer 112of the LTPS thin film transistor 130 may be formed as a single layer ofsilicon nitride (SiNx) or silicon oxide (SiOx) or a multi-layer ofsilicon nitride (SiNx) and silicon oxide (SiOx). In the gate insulationlayer 112 of the LTPS thin film transistor 130, contact holes throughwhich the source electrode 132 and the drain electrode 133 of the LTPSthin film transistor 130 are brought into contact with the source areaSA and the drain area DA of the active layer 131 of the LTPS thin filmtransistor 130, respectively, are formed.

Referring to FIG. 1, the gate electrode 134 of the LTPS thin filmtransistor 130 is disposed on the gate insulation layer 112 of the LTPSthin film transistor 130. A metal layer such as molybdenum (Mo) isformed on the gate insulation layer 112 of the LTPS thin film transistor130, and the gate electrode 134 of the LTPS thin film transistor 130 isformed by patterning the metal layer. The gate electrode 134 of the LTPSthin film transistor 130 is disposed on the gate insulation layer 112 ofthe LTPS thin film transistor 130 so as to be overlapped with thechannel area CA of the active layer 131 of the LTPS thin film transistor130.

Referring to FIG. 1, the oxide semiconductor thin film transistor 140includes the active layer 141 formed of oxide semiconductor, the gateelectrode 144 formed of conductive metal, a source electrode 142, and adrain electrode 143. As described above, the oxide semiconductor thinfilm transistor 140 can be applied to a switching thin film transistorin a pixel circuit.

Referring to FIG. 1, the gate electrode 144 of the oxide semiconductorthin film transistor 140 is formed on the gate insulation layer 112 ofthe LTPS thin film transistor 130. A metal layer such as molybdenum (Mo)is formed on the gate insulation layer 112 of the LTPS thin filmtransistor 130, and the gate electrode 144 of the oxide semiconductorthin film transistor 140 is formed by patterning the metal layer.

The gate electrode 134 of the LTPS thin film transistor 130 and the gateelectrode 144 of the oxide semiconductor thin film transistor 140 may beformed at the same process through the same process. That is, the metallayer may be formed on the gate insulation layer 112 of the LTPS thinfilm transistor 130 and then patterned to form the gate electrode 134 ofthe LTPS thin film transistor 130 and the gate electrode 144 of theoxide semiconductor thin film transistor 140 at the same process. Thus,the gate electrode 134 of the LTPS thin film transistor 130 and the gateelectrode 144 of the oxide semiconductor thin film transistor 140 may beformed on the same layer and formed of the same material to the samethickness on the same layer. Since the gate electrode 134 of the LTPSthin film transistor 130 and the gate electrode 144 of the oxidesemiconductor thin film transistor 140 are formed at the same processthrough the same process, the processing time can be reduced and thenumber of masks can be reduced. Thus, the processing costs can also bereduced. However, the present disclosure is not limited thereto. Thegate electrode of the LTPS thin film transistor 130 may be disposedunder the active layer 131, or the gate electrode of the oxidesemiconductor thin film transistor 140 may be disposed on the activelayer 141. Further, referring to FIG. 9, the gate electrode of the oxidesemiconductor thin film transistor 140 may be disposed between the gateelectrode 134 of the LTPS thin film transistor 130 and the active layer141 of the oxide semiconductor thin film transistor 140. A detailedexplanation of FIG. 9 will be provided later.

Referring to FIG. 1, the interlayer insulation layer 150 of the LTPSthin film transistor 130 is disposed on the gate electrode 134 of theLTPS thin film transistor 130 and the gate electrode 144 of the oxidesemiconductor thin film transistor 140. The interlayer insulation layer150 of the LTPS thin film transistor 130 may be formed of siliconnitride (SiNx). The interlayer insulation layer 150 functions to supplyhydrogen to the active layer 131 of the LTPS thin film transistor 130.To this end, the interlayer insulation layer 150 may be formed of afirst material including hydrogen. In one embodiment, the interlayerinsulation layer 150 is formed of silicon nitride (SiNx) having a highhydrogen content. As defined herein, hydrogen content may refer to anamount of hydrogen in a layer or a concentration of hydrogen in thelayer expressed in units of atomic percent (%) or molar percent (%). Inone embodiment, the interlayer insulation layer 150 is formed of siliconnitride (SiNx) that includes 15%-25% hydrogen content. The hydrogenationprocess is a process for filling vacancies in the active layer 131 ofthe LTPS thin film transistor 130 with hydrogen. A detailed explanationof the hydrogenation process will be provided later.

The thickness of the interlayer insulation layer 150 of the LTPS thinfilm transistor 130 may be determined on the basis of a design value ofthe LTPS thin film transistor 130. In general, the LTPS thin filmtransistor 130 has high mobility. Thus, in order to increase themobility of the LTPS thin film transistor 130, preferably, a largeamount of hydrogen may be injected into the active layer 131 of the LTPSthin film transistor 130 during the hydrogenation process. Thus, inorder to secure high mobility, the thickness of the interlayerinsulation layer 150 may also be increased. Although the thickness ofthe interlayer insulation layer 150 is increased, there is a thresholdthickness where the amount of hydrogen injected into the active layer131 of the LTPS thin film transistor 130 is saturated by thehydrogenation process. Therefore, the thickness of the interlayerinsulation layer 150 may be appropriately selected considering a targetmobility and a threshold thickness of the LTPS thin film transistor 130.Therefore, the thickness of the interlayer insulation layer 150 may havevarious values on the basis of a target mobility, a function, and anoperation of the LTPS thin film transistor 130.

In the interlayer insulation layer 150 of the LTPS thin film transistor130, the contact holes through which the source electrode 132 and thedrain electrode 133 of the LTPS thin film transistor 130 are broughtinto contact with the source area SA and the drain area DA of the activelayer 131 of the LTPS thin film transistor 130, respectively, areformed.

Referring to FIG. 1, the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 is disposed on the interlayerinsulation layer 150 of the LTPS thin film transistor 130. The gateinsulation layer 160 of the oxide semiconductor thin film transistor 140may be formed of silicon oxide (SiOx). However, materials of the gateinsulation layer 160 of the oxide semiconductor thin film transistor 140and the interlayer insulation layer 150 of the LTPS thin film transistor130 are not limited thereto. However, preferably, a material containingless hydrogen than the interlayer insulation layer 150 of the LTPS thinfilm transistor 130 may be selected as a material of the gate insulationlayer 160 of the oxide semiconductor thin film transistor 140. Further,preferably, the gate insulation layer 160 of the oxide semiconductorthin film transistor 140 may be formed of a material having a propertyor quality capable of effectively blocking hydrogen diffusion.Specifically, the gate insulation layer 160 may be formed of a secondmaterial different from a first material that blocks diffusion ofhydrogen from the interlayer insulation layer 150 to the active layer141 of the oxide semiconductor TFT 140. As described above, the gateinsulation layer 160 of the oxide semiconductor thin film transistor 140suppresses the movement of hydrogen from the insulation layer 150 of theLTPS thin film transistor 130 into the active layer 141 of the oxidesemiconductor thin film transistor 140. If the active layer 141 of theoxide semiconductor thin film transistor 140 is exposed to hydrogen,reduction may occur in the active layer 141 of the oxide semiconductorthin film transistor 140. Accordingly, there may be a change inthreshold voltage Vth of the oxide semiconductor thin film transistor140. Therefore, the gate insulation layer 160 of the oxide semiconductorthin film transistor 140 is disposed between the interlayer insulationlayer 150 of the LTPS thin film transistor 130 having a high hydrogencontent and the active layer 141 of the oxide semiconductor thin filmtransistor 140. Thus, it is possible to suppress the movement ofhydrogen from the interlayer insulation layer 150 of the LTPS thin filmtransistor 130 into the active layer 141 of the oxide semiconductor thinfilm transistor 140. Further, in a structure where the gate insulationlayer 160 of the oxide semiconductor thin film transistor 140 is indirect contact with the active layer 141 of the oxide semiconductor thinfilm transistor 140, the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 has a relatively low hydrogencontent. Therefore, an effect of hydrogen may be reduced as comparedwith a structure where the interlayer insulation layer 150 is in directcontact with the active layer 141 of the oxide semiconductor thin filmtransistor 140. In one embodiment, the gate insulation layer 160 isformed of silicon oxide (SiOx) that includes 2%-5% hydrogen content.

Thus, in the organic light emitting display device 100 according to anexemplary embodiment of the present disclosure, the gate insulationlayer 160 of the oxide semiconductor thin film transistor 140 may befurther disposed between the interlayer insulation layer 150 of the LTPSthin film transistor 130 and the active layer 141 of the oxidesemiconductor thin film transistor 140. Therefore, it is possible tomore effectively reduce diffusion of hydrogen contained in theinterlayer insulation layer 150 of the LTPS thin film transistor 130into the active layer 141 of the oxide semiconductor thin filmtransistor 140. Accordingly, reduction of the active layer 141 of theoxide semiconductor thin film transistor 140 can be minimized. Also, achange in threshold voltage Vth of the oxide semiconductor thin filmtransistor 140 can be minimized.

In the gate insulation layer 160 of the oxide semiconductor thin filmtransistor 140, the contact holes through which the source electrode 132and the drain electrode 133 of the LTPS thin film transistor 130 arebrought into connect with the source area SA and the drain area DA ofthe active layer 131 of the LTPS thin film transistor 130, respectively,are formed.

Hereinafter, an effect of suppressing hydrogen diffusion by theinterlayer insulation layer 150 of the LTPS thin film transistor 130 andthe gate insulation layer 160 of the oxide semiconductor thin filmtransistor 140 will be described in more detail with reference to FIG.2A through FIG. 2C.

FIG. 2A and FIG. 2B are cross-sectional views provided to explain aneffect of hydrogen diffusion from an interlayer insulation layer on anoxide semiconductor thin film transistor in an organic light emittingdisplay device according to a Comparative Example. FIG. 2A and FIG. 2Bare cross-sectional views of Comparative Examples where a configurationof the interlayer insulation layer 150 of the LTPS thin film transistor130 and the gate insulation layer 160 of the oxide semiconductor thinfilm transistor 140 in the organic light emitting display device 100including a multi-type thin film transistor according to an exemplaryembodiment of the present disclosure as illustrated in FIG. 1 ismodified.

Referring to FIG. 2A, in an organic light emitting display device 200Aof Comparative Example, an interlayer insulation layer 250A of the LTPSthin film transistor 130 formed of silicon nitride (SiNx) is disposed tocover the gate electrode 134 of the LTPS thin film transistor 130 andthe gate electrode 144 of the oxide semiconductor thin film transistor140. The active layer 141 of the oxide semiconductor thin filmtransistor 140 is disposed on the interlayer insulation layer 250A ofthe LTPS thin film transistor 130. Therefore, in the organic lightemitting display device 200A of Comparative Example as illustrated inFIG. 2A, the active layer 141 of the oxide semiconductor thin filmtransistor 140 is disposed to be in direct contact with the interlayerinsulation layer 250A of the LTPS thin film transistor 130 formed ofsilicon nitride (SiNx).

In a structure of the organic light emitting display device 200A ofComparative Example as described above, the active layer 141 of theoxide semiconductor thin film transistor 140 is in direct contact withthe interlayer insulation layer 250A of the LTPS thin film transistor130 formed of silicon nitride (SiNx). Thus, hydrogen may be diffusedfrom the interlayer insulation layer 250A of the LTPS thin filmtransistor 130 into the active layer 141 of the oxide semiconductor thinfilm transistor 140 (as indicated by arrows). Particularly, theactivation process and the hydrogenation process may be performed to theactive layer 131 of the LTPS thin film transistor 130 after the activelayer 141 of the oxide semiconductor thin film transistor 140 is formed.In this case, a larger amount of hydrogen may be moved from theinterlayer insulation layer 250A of the LTPS thin film transistor 130into the active layer 141 of the oxide semiconductor thin filmtransistor 140 due to high temperature applied during the activationprocess and the hydrogenation process. Thus, reduction may occur in theactive layer 141 of the oxide semiconductor thin film transistor 140 andthe threshold voltage Vth of the oxide semiconductor thin filmtransistor 140 may be changed.

Then, referring to FIG. 2B, in an organic light emitting display device200B of Comparative Example, an interlayer insulation layer 250B of theLTPS thin film transistor 130 formed of silicon oxide (SiOx) is disposedto cover the gate electrode 134 of the LTPS thin film transistor 130 andthe gate electrode 144 of the oxide semiconductor thin film transistor140. Also, a gate insulation layer 260B of the oxide semiconductor thinfilm transistor 140 formed of silicon nitride (SiNx) is disposed on theinterlayer insulation layer 250B of the LTPS thin film transistor 130.That is, in the organic light emitting display device 200B ofComparative Example as illustrated in FIG. 2B, the material of theinterlayer insulation layer 150 of the LTPS thin film transistor 130 andthe material of the gate insulation layer 160 of the oxide semiconductorthin film transistor 140 are reversed with each other as compared withthe organic light emitting display device 100 according to an embodimentof the present disclosure as illustrated in FIG. 1. Therefore, in theorganic light emitting display device 200B of Comparative Example asillustrated in FIG. 2B, the active layer 141 of the oxide semiconductorthin film transistor 140 is disposed to be in direct contact with theinterlayer insulation layer 250B of the LTPS thin film transistor 130formed of silicon nitride (SiNx).

In a structure of the organic light emitting display device 200B of theComparative Example as described above, the active layer 141 of theoxide semiconductor thin film transistor 140 is in direct contact withthe gate insulation layer 260B of the oxide semiconductor thin filmtransistor 140 formed of silicon nitride (SiNx). Thus, hydrogen may bediffused from the gate insulation layer 260B of the oxide semiconductorthin film transistor 140 into the active layer 141 of the oxidesemiconductor thin film transistor 140 (as indicated by arrows).Particularly, the activation process and the hydrogenation process maybe performed to the active layer 131 of the LTPS thin film transistor130 after the active layer 141 of the oxide semiconductor thin filmtransistor 140 is formed. In this case, a larger amount of hydrogen maybe moved from the gate insulation layer 260B of the oxide semiconductorthin film transistor 140 into the active layer 141 of the oxidesemiconductor thin film transistor 140 due to high temperature appliedduring the activation process and the hydrogenation process. Thus,reduction may occur in the active layer 141 of the oxide semiconductorthin film transistor 140 and the threshold voltage Vth of the oxidesemiconductor thin film transistor 140 may be changed.

A distance between the active layer 131 of the LTPS thin film transistor130 and the gate insulation layer 260B of the oxide semiconductor thinfilm transistor 140 formed of silicon nitride (SiNx) is greater than adistance between the active layer 131 of the LTPS thin film transistor130 and the interlayer insulation layer 150 formed of silicon nitride(SiNx) in the organic light emitting display device 100 according to anexemplary embodiment of the present disclosure illustrated in FIG. 1.Thus, when the hydrogenation process is performed to the active layer131 of the LTPS thin film transistor 130, the degree of diffusion ofhydrogen to the active layer 131 of the LTPS thin film transistor 130can be reduced.

FIG. 2C is a cross-sectional view provided to explain an effect ofhydrogen diffusion from an interlayer insulation layer on an oxidesemiconductor thin film transistor in an organic light emitting displaydevice including a multi-type thin film transistor according to anembodiment of the present disclosure. The organic light emitting displaydevice 100 illustrated in FIG. 2C is the same as the organic lightemitting display device 100 including a multi-type thin film transistorillustrated in FIG. 1.

Referring to FIG. 2C, in the organic light emitting display device 100according to an exemplary embodiment of the present disclosure, the gateinsulation layer 160 of the oxide semiconductor thin film transistor 140formed of silicon oxide (SiOx) is disposed between the interlayerinsulation layer 150 of the LTPS thin film transistor 130 formed ofsilicon nitride (SiNx) and the active layer 141 of the oxidesemiconductor thin film transistor 140. Therefore, it is possible tosuppress diffusion of hydrogen from the interlayer insulation layer 150of the LTPS thin film transistor 130 into the active layer 141 of theoxide semiconductor thin film transistor 140. Particularly, theactivation process and the hydrogenation process may be performed to theactive layer 131 of the LTPS thin film transistor 130 after the activelayer 141 of the oxide semiconductor thin film transistor 140 is formed.Even in this case, diffusion of hydrogen into the active layer 141 ofthe oxide semiconductor thin film transistor 140 (as indicated byarrows) can be suppressed. Therefore, in the organic light emittingdisplay device 100 according to an embodiment of the present disclosure,the interlayer insulation layer 150 of the LTPS thin film transistor 130and the gate insulation layer 160 of the oxide semiconductor thin filmtransistor 140 having a structure and a lamination relationshipdifferent from the conventional organic light emitting display devices200A and 200B of Comparative Examples are used. Thus, the amount ofhydrogen diffused into the active layer 141 of the oxide semiconductorthin film transistor 140 can be reduced. Therefore, a change inthreshold voltage (Vth) of the oxide semiconductor thin film transistor140 can be minimized.

In FIG. 1 and FIG. 2C, the interlayer insulation layer 150 of the LTPSthin film transistor 130 is defined as a single layer formed of siliconnitride (SiNx) and the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 is defined as a single layerformed of silicon oxide (SiOx). However, the interlayer insulation layer150 of the LTPS thin film transistor 130 may include a lower layerformed of silicon nitride (SiNx) and an upper layer formed of siliconoxide (SiOx) and the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 may be omitted. Otherwise, theinterlayer insulation layer 150 of the LTPS thin film transistor 130 maybe omitted and the gate insulation layer 160 of the oxide semiconductorthin film transistor 140 may include a lower layer formed of siliconnitride (SiNx) and an upper layer formed of silicon oxide (SiOx).

In some exemplary embodiments, the interlayer insulation layer 150 ofthe LTPS thin film transistor 130 may be patterned. That is, in order tominimize diffusion of hydrogen from the interlayer insulation layer 150into the active layer 141 of the oxide semiconductor thin filmtransistor 140, the interlayer insulation layer 150 may be patterned tobe overlapped only with the LTPS thin film transistor 130. Therefore,the area of the interlayer insulation layer 150 having a relatively highhydrogen content is reduced. Thus, exposure of the active layer 141 ofthe oxide semiconductor thin film transistor 140 to hydrogen can beminimized.

Referring to FIG. 1 again, the active layer 141 of the oxidesemiconductor thin film transistor 140 is disposed on the gateinsulation layer 160 of the oxide semiconductor thin film transistor140. The active layer 141 of the oxide semiconductor thin filmtransistor 140 is formed of a metal oxide, and may be formed of variousmetal oxides such as IGZO. The active layer 141 of the oxidesemiconductor thin film transistor 140 may be formed by depositing ametal oxide on the gate insulation layer 160 of the oxide semiconductorthin film transistor 140, performing a heat treatment thereto forstabilization, and patterning the metal oxide.

Referring to FIG. 1, the source electrode 142 and the drain electrode143 are formed directly on the active layer 141 of the oxidesemiconductor thin film transistor 140. The active layer 141 of theoxide semiconductor thin film transistor 140 is electrically connectedto the source electrode 142 and the drain electrode 143 through ohmiccontact. Therefore, the active layer 141 of the oxide semiconductor thinfilm transistor 140 does not necessarily require a conducting process. Amanufacturing process of the active layer 141 of the oxide semiconductorthin film transistor 140 will be described later.

Referring to FIG. 1, the source electrode 132 and the drain electrode133 of the LTPS thin film transistor 130 and the source electrode 142and the drain electrode 143 of the oxide semiconductor thin filmtransistor 140 are disposed on the gate insulation layer 160 of theoxide semiconductor thin film transistor 140 on which the active layer141 of the oxide semiconductor thin film transistor 140 is disposed. Thesource electrode 132 and the drain electrode 133 of the LTPS thin filmtransistor 130 and the source electrode 142 and the drain electrode 143of the oxide semiconductor thin film transistor 140 may be formed of aconductive metal material, and may be formed as a three-layer structureincluding, e.g., titanium (Ti)/aluminum (Al)/titanium (Ti).

The source electrode 132 and the drain electrode 133 of the LTPS thinfilm transistor 130 are respectively connected to the source area SA andthe drain area DA of the active layer 131 of the LTPS thin filmtransistor 130 through the contact holes formed in the gate insulationlayer 112 of the LTPS thin film transistor 130, the interlayerinsulation layer 150 of the LTPS thin film transistor 130, and the gateinsulation layer 160 of the oxide semiconductor thin film transistor140. Further, the source electrode 142 and the drain electrode 143 ofthe oxide semiconductor thin film transistor 140 are respectivelyconnected to both sides of the active layer 141 of the oxidesemiconductor thin film transistor 140.

The source electrode 132 and the drain electrode 133 of the LTPS thinfilm transistor 130 and the source electrode 142 and the drain electrode143 of the oxide semiconductor thin film transistor 140 may be formed atthe same process through the same process. That is, a source/drainmaterial layer is formed on the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 and the source/drain materiallayer is patterned to form the source electrode 132 and the drainelectrode 133 of the LTPS thin film transistor 130 and the sourceelectrode 142 and the drain electrode 143 of the oxide semiconductorthin film transistor 140 at the same process. Thus, the source electrode132 and the drain electrode 133 of the LTPS thin film transistor 130 andthe source electrode 142 and the drain electrode 143 of the oxidesemiconductor thin film transistor 140 may be formed of the samematerial to the same thickness. Since the source electrode 132 and thedrain electrode 133 of the LTPS thin film transistor 130 and the sourceelectrode 142 and the drain electrode 143 of the oxide semiconductorthin film transistor 140 are formed at the same process through the sameprocess, the processing time can be reduced and the number of masks canbe reduced. Thus, the processing costs can also be reduced.

Referring to FIG. 1, the passivation layer 170 is disposed on the LTPSthin film transistor 130 and the oxide semiconductor thin filmtransistor 140. The passivation layer 170 is an insulation layerconfigured to protect the LTPS thin film transistor 130 and the oxidesemiconductor thin film transistor 140. Further, the passivation layer170 may also function to block hydrogen diffused from above the LTPSthin film transistor 130 and the oxide semiconductor thin filmtransistor 140. In the passivation layer 170, a contact hole throughwhich the source electrode 132 of the LTPS thin film transistor 130 isexposed is formed.

The passivation layer 170 will be described in more detail withreference to FIG. 3A and FIG. 3B.

FIG. 3A is a cross-sectional view provided to explain an effect ofhydrogen diffused from an encapsulation unit on an oxide semiconductorthin film transistor in an organic light emitting display deviceincluding a multi-type thin film transistor according to an embodimentof the present disclosure. The organic light emitting display device 100including a multi-type thin film transistor illustrated in FIG. 3A isthe same as the organic light emitting display device 100 illustrated inFIG. 1.

Referring to FIG. 3A, the encapsulation unit 190 is disposed on thepassivation layer 170. The encapsulation unit 190 protects the organiclight emitting element 180 vulnerable to moisture so as not to beexposed to moisture. The encapsulation unit 190 may have a structure inwhich inorganic layers 191 and 193 and an organic layer 192 arealternately laminated. The encapsulation unit 190 illustrated in FIG. 3Ahas a structure in which a first inorganic layer 191, an organic layer192, and a second inorganic layer 193 are laminated in sequence. In thiscase, the first inorganic layer 191 and the second inorganic layer 193may be formed of an inorganic material such as silicon nitride (SiNx) toeffectively suppress permeation of moisture into the organic lightemitting element 180. Herein, the first inorganic layer 191 and thesecond inorganic layer 193 need to be formed on the organic lightemitting element 180, but the organic light emitting element 180 is veryvulnerable to high temperature. Therefore, the first inorganic layer 191and the second inorganic layer 193 are formed by a low-temperatureprocess such as low-temperature deposition. The first inorganic layer191 and the second inorganic layer 193 formed by a low-temperatureprocess have a higher hydrogen content than an inorganic layer formed bya high-temperature process. Therefore, after the organic light emittingdisplay device 100 is manufactured, hydrogen can be diffused (asindicated by arrows) from the first inorganic layer 191 and the secondinorganic layer 193 of the encapsulation unit 190 as illustrated in FIG.3A. Then, the diffused hydrogen can reach the active layer 141 of theoxide semiconductor thin film transistor 140. If hydrogen is diffusedinto the active layer 141 of the oxide semiconductor thin filmtransistor 140 as such, reduction may occur in the active layer 141 ofthe oxide semiconductor thin film transistor 140 and the thresholdvoltage Vth of the oxide semiconductor thin film transistor 140 may bechanged. Thus, in the organic light emitting display device 100according to an embodiment of the present disclosure, the passivationlayer 170 is formed to have a specific lamination structure. Thepassivation layer 170 will be described in more detail with reference toFIG. 3B.

FIG. 3B is an enlarged view of an area A of FIG. 3A.

Referring to FIG. 3B, the passivation layer 170 has a multi-layerstructure including a first passivation layer 171 and a secondpassivation layer 172. Specifically, the first passivation layer 171 isdisposed to cover the active layer 141 of the oxide semiconductor thinfilm transistor 140, the source electrode 132 and the drain electrode133 of the LTPS thin film transistor 130, and the gate insulation layer160 of the oxide semiconductor thin film transistor 140. Further, thesecond passivation layer 172 is disposed on the first passivation layer171. Meanwhile, the first passivation layer 171 may be formed of siliconoxide (SiOx) and the second passivation layer 172 may be formed ofsilicon nitride (SiNx). The passivation layer 170 protects the oxidesemiconductor thin film transistor 140 and the LTPS thin film transistor130 against moisture or hydrogen permeating from above the passivationlayer 170.

A typically used passivation layer is formed as a single layer ofsilicon nitride (SiNx). Meanwhile, the passivation layer 170 is disposedin direct contact with the active layer 141 of the oxide semiconductorthin film transistor 140. Therefore, hydrogen contained in siliconnitride (SiNx) may be diffused into the active layer 141 of the oxidesemiconductor thin film transistor 140. Thus, in the organic lightemitting display device 100 according to an embodiment of the presentdisclosure, the first passivation layer 171 formed of silicon oxide(SiOx) is disposed in contact with the active layer 141 of the oxidesemiconductor thin film transistor 140. Also, the second passivationlayer 172 formed of silicon nitride (SiNx) is disposed on the firstpassivation layer 171. Thus, it is possible to effectively suppresshydrogen diffused from above the passivation layer 170.

The following Table 1 is provided to explain an effect of suppressinghydrogen diffusion by a passivation layer according to ComparativeExample and the passivation layer 170 of the organic light emittingdisplay device 100 according to an exemplary embodiment of the presentdisclosure.

TABLE 1 Hydrogen Comparative plasma Example Example 1 Example 2 processBefore After Before After Before After Vth average 0.27 V −9.30 V 0.08 V−4.63 V 0.53 V 0.46 V Vth variation Δ 9.57 V Δ 4.71 V Δ 0.07 V

Comparative Example shows that the passivation layer is a single layer,and Examples 1 and 2 show that the passivation layer is a double layer.Further, in the Comparative Example, the passivation layer is formed ofsilicon oxide (SiOx) having a thickness of 2000 Å. In Examples 1 and 2,the first passivation layer 171 is formed of silicon oxide (SiOx) havinga thickness of 1000 Å and the second passivation layer 172 is formed ofsilicon nitride (SiNx) having a thickness of 1000 Å. Meanwhile, inExample 1, when the second passivation layer 172 was deposited, a silane(SiH₄) gas was not injected as an injection source into the chamber. InExample 2, when the second passivation layer 172 was deposited, a silane(SiH₄) gas and an ammonia (NH₃) gas were injected as an injection sourceinto the chamber and a ratio of SiH₄:NH₃ was controlled to 1:6.5.Further, the silicon oxide (SiOx) layer and the silicon nitride (SiNx)layer are formed by PECVD. In all of Comparative Example and Examples 1and 2, the oxide semiconductor thin film transistor 140 was disposedunder the passivation layer 170. Further, the oxide semiconductor thinfilm transistor 140 was manufactured such that a channel area has awidth of 6 μm and a length of 6 μm. As described above, after thepassivation layer 170 was formed on the oxide semiconductor thin filmtransistor 140, a hydrogen plasma process was performed to provide thesame effect as diffusion of moisture from the encapsulation unit 190.The hydrogen plasma process was performed under the processingconditions of 5 kW, 3000 sccm, and 60 sec. Before and after the hydrogenplasma process, the threshold voltage Vth of the oxide semiconductorthin film transistor 140 was measured from the samples of ComparativeExample and Examples 1 and 2. Further, an average value of the thresholdvoltages Vth before the hydrogen plasma process and an average value ofthe threshold voltages Vth after the hydrogen plasma process are shown.Also, a variation between the average values was also shown. In thiscase, the samples are 20 oxide semiconductor thin film transistorsformed on a single mother substrate.

Referring to Table 1, it was confirmed that in Comparative Example, thethreshold voltage (Vth) variation before and after the hydrogen plasmaprocess was as high as A 9.57 V. In Comparative Example, only a singlelayer formed of silicon oxide (SiOx) was used as the passivation layer170 to suppress hydrogen diffused from the encapsulation unit 190.However, it can be seen from Table 1 that if only the single layerformed of silicon oxide (SiOx) constitutes the passivation layer 170,the threshold voltage Vth of the oxide semiconductor thin filmtransistor 140 is greatly changed after the hydrogen plasma process.

In Example 1, the passivation layer 170 includes the first passivationlayer 171 formed of silicon oxide (SiOx) and the second passivationlayer 172 disposed on the first passivation layer 171 and formed ofsilicon nitride (SiNx) to solve the above-described problem. Further, inorder to minimize diffusion of hydrogen from the second passivationlayer 172 formed of silicon nitride (SiNx), when the second passivationlayer 172 was deposited, only a silane (SiH₄) gas and a nitrogen (N₂)gas were used as an injection source but an ammonia (NH₃) gas was notused. The injection source refers to a material to be injected into achamber of a PECVD system, and a thin film is formed by a reactionbetween gases decomposed by plasma. Referring to Table 1 in regard toExample 1, it can be seen that the threshold voltage (Vth) variation wasgreatly decreased to Δ 4.71 V as compared with Comparative Example.Thus, it can be seen that the passivation layer 170 of the organic lightemitting display device 100 according to an embodiment of the presentdisclosure can effectively suppress hydrogen diffused from theencapsulation unit 190.

A structure or materials used in Example 2 were the same as those usedin Example 1 except that when the second passivation layer 172 wasdeposited, a silane (SiH₄) gas, a nitrogen (N₂) gas, and an ammonia(NH₃) gas were used as an injection source and a flow rate ratio of thesilane (SiH₄) gas to the ammonia (NH₃) gas was 1:6.5. Referring to Table1 in regard to Example 2, it can be seen that the threshold voltage(Vth) variation was greatly decreased to Δ 0.07 V as compared withComparative Example. Thus, it can be seen that the passivation layer 170of the organic light emitting display device 100 according to anembodiment of the present disclosure can effectively suppress hydrogendiffused from the encapsulation unit 190.

Also, in Example 1 where an ammonia (NH₃) gas is not used as theinjection source, the second passivation layer 172 formed of siliconnitride (SiNx) has a columnar crystal shape, so that a film density ofthe second passivation layer 172 is decreased. In Example 2 where asilane (SiH₄) gas and an ammonia (NH₃) gas are used as the injectionsource, a film density of the second passivation layer 172 is increased.

The second passivation layer 172 in Example 2 has a high film densityand is excellent in blocking hydrogen as compared with the secondpassivation layer 172 in Example 1. Referring to Table 1, the thresholdvoltage (Vth) variation of the oxide semiconductor thin film transistor140 is lower in Example 2 than in Example 1. Thus, the method of using asilane (SiH₄) gas and an ammonia (NH₃) gas as the injection source whenthe second passivation layer 172 is deposited is more effective in termsof the reliability of the oxide semiconductor thin film transistor 140.Preferably, a ratio of the silane (SiH₄) gas to the ammonia (NH₃) gasmay be 1:4.5 or more. If the ratio of the silane (SiH₄) gas to theammonia (NH₃) gas is less than 1:4.5, the threshold voltage Vth of theoxide semiconductor thin film transistor 140 may be changed. The unit ofthe flow rate of the silane (SiH₄) gas to the ammonia (NH₃) gas used asthe injection source is sccm (Standard Cubic Centimeter per Minute;cm³/min) which refers to the amount of 1 cc gas flowing per minute.

Referring to FIG. 1 again, the storage capacitor 120 is disposed on thesubstrate 110. The storage capacitor 120 includes a first electrode 121disposed on the buffer layer 111 and a second electrode 122 formed onthe gate insulation layer 112 of the LTPS thin film transistor 130. Thefirst electrode 121 of the storage capacitor 120 may be formed of thesame material at the same process as the active layer 131 of the LTPSthin film transistor 130. Thus, the first electrode 121 may be disposedon a same layer as the active layer 131. A conducting process may beapplied to the first electrode 121 so as to function as an electrode ofthe storage capacitor 120. Further, the second electrode 122 of thestorage capacitor 120 may be formed of the same material at the sameprocess as the gate electrode 134 of the LTPS thin film transistor 130.Thus, the second electrode 122 may be disposed on a same layer as thegate electrode 134. Therefore, the storage capacitor 120 can be formedduring a manufacturing process of the LTPS thin film transistor 130without any additional processes, which is efficient in terms of theprocessing costs and the processing time. In order to increase acapacitance of the storage capacitor 120, a third electrode of thestorage capacitor 120 may be further formed on the gate insulation layer160 of the oxide semiconductor thin film transistor 140. The thirdelectrode may be formed of the same material through the same process asthe active layer 141 of the oxide semiconductor thin film transistor140. Thus, the third electrode may be disposed on a same layer as theactive layer 141. Otherwise, the third electrode may be formed of thesame material through the same process as the source electrode 132 andthe drain electrode 133 of the LTPS thin film transistor 130 or thesource electrode 142 and the drain electrode 143 of the oxidesemiconductor thin film transistor 140.

Referring to FIG. 1, the overcoating layer 113 is disposed on thepassivation layer 170. The overcoating layer 113 is an insulation layerconfigured to flatten upper parts of the oxide semiconductor thin filmtransistor 140 and the LTPS thin film transistor 130 and may be formedof an organic material. FIG. 1 illustrates that all of upper parts ofvarious insulation layers under the overcoating layer 113 are flattened,for convenience in explanation. However, actually, there may be stepscaused by the components of the oxide semiconductor thin film transistor140 and the LTPS thin film transistor 130 or foreign materials. Thus, byflattening the upper parts of the oxide semiconductor thin filmtransistor 140 and the LTPS thin film transistor 130 or minimizing stepson a surface on which the organic light emitting element 180 isdisposed, the organic light emitting element 180 can be formed with morereliability. Further, the overcoating layer 113 may reduce a capacitancebetween the source electrode 132 of the LTPS thin film transistor 130and an anode 181. In the overcoating layer 113, the contact hole throughwhich the source electrode 132 of the LTPS thin film transistor 130 isexposed and connected to the anode 181 is formed.

Referring to FIG. 1, the organic light emitting element 180 is disposedon the overcoating layer 113. The organic light emitting element 180includes the anode 181 formed on the overcoating layer 113 andelectrically connected to the source electrode 132 of the LTPS thin filmtransistor 130, an organic layer 182 disposed on the anode 181, and acathode 183 formed on the organic layer 182. Further, the anode 181 mayinclude a reflective layer configured to reflect a light emitted fromthe organic layer 182 toward the encapsulation unit 190 and atransparent conductive layer configured to supply holes to the organiclayer 182. The organic layer 182 is configured to emit a light of aspecific color and may include one of a red organic emission layer, agreen organic emission layer, a blue organic emission layer, and a whiteorganic emission layer. If the organic layer 182 includes the whiteorganic emission layer, a color filter configured to convert a whitelight from the white organic emission layer into a light of a differentcolor may be disposed on the organic light emitting element 180.Further, the organic layer 182 may further include various organiclayers, such as a hole transport layer, a hole injection layer, anelectron injection layer, an electron transport layer, etc., in additionto the organic emission layer.

Referring to FIG. 1, a bank 114 is disposed on the overcoating layer 113so as to cover both ends of the anode 181. The bank 114 defines a pixelarea by separating adjacent pixel areas in a display area.

FIG. 4A is a cross-sectional view provided to explain an organic lightemitting display device including a multi-type thin film transistoraccording to another embodiment of the present disclosure. FIG. 4B is anenlarged view of an area A of FIG. 4A. An organic light emitting displaydevice 400 illustrated in FIG. 4A and FIG. 4B is substantially the sameas the organic light emitting display device 100 illustrated in FIG. 1except that a gate insulation layer 460 of the oxide semiconductor thinfilm transistor 140 and a passivation layer 470 are modified. Therefore,redundant description thereof will be omitted.

Referring to FIG. 4A and FIG. 4B, the gate insulation layer 460 of theoxide semiconductor thin film transistor 140 includes a first gateinsulation layer 461 and a second gate insulation layer 462 on the firstgate insulation layer 461. Since the second gate insulation layer 462 isdisposed on the first gate insulation layer 461, the second gateinsulation layer 462 is in contact with the active layer 141 of theoxide semiconductor thin film transistor 140. In this case, the firstgate insulation layer 461 and the second gate insulation layer 462 maybe formed of silicon oxide (SiOx), and the second gate insulation layer462 may have a lower hydrogen content than the first gate insulationlayer 461. Thus, a portion of the gate insulation layer 460 contactingthe oxide semiconductor active layer 141 (e.g., portion corresponding tothe second gate insulation layer 462) may have a lower hydrogen contentthan a portion of the gate insulation layer 460 spaced apart from theactive layer 141 (e.g., corresponding to the first gate insulation layer461).

The amount of an injection source used for depositing the first gateinsulation layer 461 and the second gate insulation layer 462 may beadjusted to form the first gate insulation layer 461 and the second gateinsulation layer 462 different from each other in hydrogen content asdescribed above. For example, the amount of a silane (SiH₄) gas may beadjusted. That is, the amount of a silane (SiH₄) gas used for depositingthe second gate insulation layer 462 may be adjusted to be smaller thanthe amount of a silane (SiH₄) gas used for depositing the first gateinsulation layer 461. Then, a deposition process of the second gateinsulation layer 462 is performed through as low-hydrogen process. Theamount of a silane (SiH₄) gas in the deposition process of the secondgate insulation layer 462 is set to be smaller than the amount of asilane (SiH₄) gas in a deposition process of the first gate insulationlayer 461. Thus, the deposition process of the second gate insulationlayer 462 requires a longer time than the deposition process of thefirst gate insulation layer 461. Therefore, in the deposition process ofthe second gate insulation layer 462, atoms are deposited more densely,so that the second gate insulation layer 462 has a higher film densitythan the first gate insulation layer 461. Thus, a portion of the gateinsulation layer 460 contacting the active layer 141 (e.g.,corresponding to the second gate insulation layer 462) may have a higherfilm density than a portion of the gate insulation layer 460 spacedapart from the active layer 141 (e.g., corresponding to the first gateinsulation layer 461). Accordingly, even if the first gate insulationlayer 461 and the second gate insulation layer 462 are formed of thesame material, the second gate insulation layer 462 has a higher filmdensity than the first gate insulation layer 461. Thus, it is possibleto more efficiently suppress diffusion of hydrogen into the active layer141 of the oxide semiconductor thin film transistor 140 from under theoxide semiconductor thin film transistor 140. Further, if the amount ofa silane (SiH₄) gas used for depositing the second gate insulation layer462 is adjusted in order for the second gate insulation layer 462 tohave a lower hydrogen content than the first gate insulation layer 461,the degree of exposure of the active layer 141 of the oxidesemiconductor thin film transistor 140 to hydrogen can be furtherreduced. Therefore, reduction of the active layer 141 of the oxidesemiconductor thin film transistor 140 and a change in threshold voltageVth of the oxide semiconductor thin film transistor 140 can beminimized. Further, a bias temperature stress (BTS) of the oxidesemiconductor thin film transistor 140 can also be improved.

Meanwhile, electrons may be trapped in an interface between the gateinsulation layer 460 of the oxide semiconductor thin film transistor 140and the active layer 141 of the oxide semiconductor thin film transistor140. In order to solve such an electron trap, a layer having a high filmdensity may be disposed under the active layer 141 of the oxidesemiconductor thin film transistor 140. Therefore, the second gateinsulation layer 462 having a higher film density than the first gateinsulation layer 461 may be disposed under the active layer 141 of theoxide semiconductor thin film transistor 140 to suppress theabove-described electron trap. Meanwhile, the threshold voltage Vth ofthe oxide semiconductor thin film transistor 140 can be controlled bymodifying the composition of the first gate insulation layer 461.Therefore, the gate insulation layer 460 may be formed as a multi-layerstructure as described above.

The passivation layer 470 may include a third passivation layer 473, afirst passivation layer 171 on the third passivation layer 473, and thesecond passivation layer 172 on the first passivation layer 171. Sincethe third passivation layer 473 is disposed under the first passivationlayer 171, the third passivation layer 473 is in contact with the activelayer 141 of the oxide semiconductor thin film transistor 140. In thiscase, the third passivation layer 473 and the first passivation layer171 may be formed of silicon oxide (SiOx), and the third passivationlayer 473 may have a lower hydrogen content than the first passivationlayer 171. Thus, a portion of the passivation layer 470 contacting theoxide semiconductor active layer 141 (e.g., portion corresponding to thethird passivation layer 473) may have a lower hydrogen content than aportion of the passivation layer 470 spaced apart from the active layer141 (e.g., corresponding to the first passivation layer 171).

The amount of an injection source used for depositing the firstpassivation layer 171 and the third passivation layer 473 may beadjusted to form the first passivation layer 171 and the thirdpassivation layer 473 different from each other in hydrogen content asdescribed above. For example, the amount of a silane (SiH₄) gas may beadjusted. That is, the amount of a silane (SiH₄) gas used for depositingthe third passivation layer 473 may be adjusted to be smaller than theamount of a silane (SiH₄) gas used for depositing the first passivationlayer 171. Then, a deposition process of the third passivation layer 473is performed through as low-hydrogen process. The amount of a silane(SiH₄) gas in the deposition process of the third passivation layer 473is set to be smaller than the amount of a silane (SiH₄) gas in adeposition process of the first passivation layer 171. Thus, thedeposition process of the third passivation layer 473 requires a longertime than the deposition process of the first passivation layer 171.Therefore, in the deposition process of the third passivation layer 473,atoms are deposited more densely, so that the third passivation layer473 has a higher film density than the first passivation layer 171.Accordingly, even if the first passivation layer 171 and the thirdpassivation layer 473 are formed of the same material, the thirdpassivation layer 473 has a higher film density than the firstpassivation layer 171. Thus, a portion of the passivation layer 470contacting the oxide semiconductor active layer 141 (e.g., portioncorresponding to the third passivation layer 473) may have a lowerhydrogen content than a portion of the passivation layer 470 spacedapart from the active layer 141 (e.g., corresponding to the firstpassivation layer 171). Thus, it is possible to further suppressdiffusion of hydrogen into the active layer 141 of the oxidesemiconductor thin film transistor 140 from above the oxidesemiconductor thin film transistor 140. Further, the third passivationlayer 473 has a lower hydrogen content than the first passivation layer171. Thus, when the third passivation layer 473 is disposed under thefirst passivation layer 171, exposure of the active layer 141 of theoxide semiconductor thin film transistor 140 to hydrogen can beminimized. Therefore, reduction of the active layer 141 of the oxidesemiconductor thin film transistor 140 and a change in threshold voltageVth of the oxide semiconductor thin film transistor 140 can besuppressed. Further, the bias temperature stress (BTS) of the oxidesemiconductor thin film transistor 140 can also be improved.

FIG. 5 is a cross-sectional view provided to explain an organic lightemitting display device including a multi-type thin film transistoraccording to yet another embodiment of the present disclosure. Anorganic light emitting display device 500 illustrated in FIG. 5 issubstantially the same as the organic light emitting display device 100illustrated in FIG. 1 except that an intermediate electrode 519 isadded, a storage capacitor 520 is modified, and an overcoating layerincludes two layers 513 and 515. Therefore, redundant descriptionthereof will be omitted.

Referring to FIG. 5, in the organic light emitting display device 500according to yet another embodiment of the present disclosure,additional metal layers 523, 524, and 519 are added, so that acapacitance of the storage capacitor 520 can be increased and a lineresistance can be reduced. Also, the width of a non-display area (bezelarea) can be reduced.

The storage capacitor 520 includes the first electrode 121, the secondelectrode 122, a third electrode 523, and a fourth electrode 524laminated in sequence. The first electrode 121 of the storage capacitor520 may be formed of the same material at the same process as the activelayer 131 of the LTPS thin film transistor 130. The second electrode 122of the storage capacitor 520 may be formed of the same material at thesame process as the gate electrode 144 of the oxide semiconductor thinfilm transistor 140 and the gate electrode 134 of the LTPS thin filmtransistor 130. Also, the third electrode 523 of the storage capacitor520 may be formed of the same material at the same process as the sourceelectrode 142 and the drain electrode 143 of the oxide semiconductorthin film transistor 140 and the source electrode 132 and the drainelectrode 133 of the LTPS thin film transistor 130. The fourth electrode524 of the storage capacitor 520 may be formed on a first overcoatinglayer 513 using an additional metal material. The first overcoatinglayer 513 may be formed of the same material as the overcoating layer113 illustrated in FIG. 1 and may reduce a parasitic capacitance formedbetween the source electrode 132 of the LTPS thin film transistor 130and the intermediate electrode 519. Further, in the storage capacitor520, a capacitor using the first electrode 121 and the second electrode122 as both terminals, a capacitor using the second electrode 122 andthe third electrode 523 as both terminals, and a capacitor using thethird electrode 523 and the fourth electrode 524 as both terminals maybe connected in parallel with each other. Therefore, a capacitance ofthe storage capacitor 520 can be increased.

Then, the intermediate electrode 519 is disposed on the firstovercoating layer 513. The intermediate electrode 519 is connected tothe source electrode 132 of the LTPS thin film transistor 130 through acontact hole in the passivation layer 170 and the first overcoatinglayer 513. A second overcoating layer 515 configured to flatten upperparts of the intermediate electrode 519 and the fourth electrode 524 ofthe storage capacitor 520 is disposed on the intermediate electrode 519and the fourth electrode 524 of the storage capacitor 520. The secondovercoating layer 515 may perform the same function as the overcoatinglayer 113 illustrated in FIG. 1. The intermediate electrode 519 may beformed of the same additional metal material as the fourth electrode 524of the storage capacitor 520. In the organic light emitting displaydevice 500 according to yet another embodiment of the presentdisclosure, a line resistance in a display area where a plurality ofpixels is disposed can be reduced using the additional metal material.That is, lines configured to transfer the same signal may be formed as amulti-layer structure using the additional metal material. Therefore,the lines can be connected in parallel, so that the line resistance canbe reduced.

Likewise, a line resistance of various lines disposed in a non-displayarea can also be reduced. The lines disposed in the non-display area areformed of the same material as various electrodes and lines disposed inthe display area. Thus, the various lines disposed in the non-displayarea are limited in design, and there is a limit to reduction in lineresistance of the lines. However, in the organic light emitting displaydevice 500 according to yet another embodiment of the presentdisclosure, the additional metal material additionally used in thedisplay area is also disposed in the non-display area. Thus, the variouslines disposed in the non-display area may be formed as a multi-layerstructure configured to transfer the same signal through a plurality oflayers. Therefore, the line resistance can be reduced. Further, in theorganic light emitting display device 500 according to yet anotherembodiment of the present disclosure, the additional metal materialadditionally used in the display area is also disposed in thenon-display area. Thus, lines configured to transfer different signalsmay be disposed to be overlapped with each other. Therefore, the widthof the non-display area can be reduced, so that the organic lightemitting display device 500 with an improved narrow bezel can beprovided.

In some embodiments, an additional passivation layer configured toprotect the intermediate electrode 519 and the fourth electrode 524 ofthe storage capacitor 520 may be disposed on the first overcoating layer513 so as to cover the intermediate electrode 519 and the fourthelectrode 524 of the storage capacitor 520. In the organic lightemitting display device 500 illustrated in FIG. 5, the two overcoatinglayers 513 and 515 are disposed continuously on the passivation layer170. However, in some embodiments, a second passivation layer may bedisposed instead of the first overcoating layer 513 illustrated in FIG.5, so that two passivation layers may be disposed continuously.

FIG. 6A is a cross-sectional view provided to explain an effect of asubstrate and a buffer layer in an organic light emitting display deviceincluding a multi-type thin film transistor according to an embodimentof the present disclosure. The organic light emitting display device 100illustrated in FIG. 6A is substantially the same as the organic lightemitting display device 100 illustrated in FIG. 1. Therefore, redundantdescription thereof will be omitted.

As described above, the substrate 110 of the organic light emittingdisplay device 100 may be formed of a plastic material such as polyimide(PI). The buffer layer 111 containing silicon nitride (SiNx) may bedisposed on the substrate 110. Therefore, hydrogen or moisture from thesubstrate 110 or the buffer layer 111 may move upwards and affect theactive layer 131 of the LTPS thin film transistor 130 and the activelayer 141 of the oxide semiconductor thin film transistor 140.

Further, if the substrate 110 is formed of a plastic material, asupporting substrate for supporting the substrate 110 during themanufacturing process is bonded to a lower side of the substrate 110. Inthis case, a sacrificial layer is disposed between the substrate 110 andthe supporting substrate. After the manufacturing process is completed,the substrate 110 and the supporting substrate may be separated througha laser release process. The active layer 131 of the LTPS thin filmtransistor 130 and the active layer 141 of the oxide semiconductor thinfilm transistor 140 formed on the substrate 110 may be damaged by alaser irradiated during the laser release process.

Further, due to a current drop caused by the substrate 110 and thesacrificial layer, the threshold voltage Vth of the LTPS thin filmtransistor 130 and the oxide semiconductor thin film transistor 140 maybe changed. Specifically, a negative charge trap occurs in thesacrificial layer due to the laser and a light incident from theoutside, and positive charges from the plastic material, e.g., polyimide(PI), in the substrate 110 move toward the sacrificial layer. Therefore,a potential on a surface of the substrate 110 is increased and thethreshold voltage Vth of the LTPS thin film transistor 130 and the oxidesemiconductor thin film transistor 140 may be shifted in a positivedirection. Such a shift of the threshold voltage Vth decreases thereliability of the organic light emitting display device 100.

Referring to FIG. 6A, in the oxide semiconductor thin film transistor140, the gate electrode 144 is disposed under the active layer 141.Therefore, the gate electrode 144 can block hydrogen or moisturedescribed above and also block the laser irradiated during the laserrelease process. Further, a shift of the threshold voltage Vth of theoxide semiconductor thin film transistor which may occur when thepotential on the surface of the substrate 110 is increased can also besuppressed. However, the active layer 131 of the LTPS thin filmtransistor 130 illustrated in FIG. 6A is exposed to all of theabove-described dangers. Thus, the organic light emitting display device100 according to various embodiments of the present disclosure mayfurther include a bottom shield metal (BSM).

FIG. 6B and FIG. 6C are cross-sectional views of organic light emittingdisplay devices each including a multi-type thin film transistoraccording to various embodiments of the present disclosure. An organiclight emitting display device 600B illustrated in FIG. 6B issubstantially the same as the organic light emitting display device 100illustrated in FIG. 1 except that a BSM 617 and an active buffer 618 arefurther provided. Therefore, redundant description thereof will beomitted. An organic light emitting display device 600C illustrated inFIG. 6C is substantially the same as the organic light emitting displaydevice 100 illustrated in FIG. 1 except that the BSM 617 and the activebuffer 618 are further provided and the source electrode 132 of the LTPSthin film transistor 130 is connected to the BSM 617. Therefore,redundant description thereof will be omitted.

Referring to FIG. 6B, the BSM 617 is disposed on the buffer layer 111.The BSM 617 may be disposed on the buffer layer 111 so as to beoverlapped with the active layer 131 of the LTPS thin film transistor130. In a cross-sectional view, the BSM 617 may have a greater widththan the active layer 131 of the LTPS thin film transistor 130. The BSM617 may be formed of various metal materials. In the organic lightemitting display device 600B illustrated in FIG. 6B, the BSM 617 may befloated, so that a voltage may not be applied to the BSM 617.

The active buffer 618 configured to insulate the BSM 617 from the activelayer 131 of the LTPS thin film transistor 130 is disposed on the BSM617. The active buffer 618 may be formed of the same material as thebuffer layer 111. For example, the active buffer 618 may be formed as asingle layer of silicon nitride (SiNx) or silicon oxide (SiOx) or amulti-layer including silicon nitride (SiNx) and silicon oxide (SiOx)laminated alternately.

Referring to FIG. 6C, the BSM 617 is disposed on the buffer layer 111and the active buffer 618 is disposed on the BSM 617. Further, a sourceelectrode 632 of an LTPS thin film transistor 630 is connected to theBSM 617 through a contact hole. Therefore, the same voltage is appliedto the BSM 617 and the source electrode 632 of the LTPS thin filmtransistor 630. FIG. 6C illustrates that the BSM 617 is connected to thesource electrode 632 of the LTPS thin film transistor 630. However, theBSM 617 may be connected to the gate electrode 134 of the LTPS thin filmtransistor 630 or the drain electrode 133 of the LTPS thin filmtransistor 630. Accordingly, the same voltage may be applied to the BSM617 and the gate electrode 134 of the LTPS thin film transistor 630 orto the BSM 617 and the drain electrode 133 of the LTPS thin filmtransistor 630. Otherwise, a desired constant voltage may be applied tothe BSM 617 through a separate line for applying a constant voltage.

In the organic light emitting display devices 600B and 600C according tovarious embodiments of the present disclosure, the BSM 617 floated asillustrated in FIG. 6B may be used or the BSM 617 configured to beapplied with a specific voltage as illustrated in FIG. 6C may be furtherincluded. Thus, the laser irradiated during the laser release processand hydrogen or moisture can be blocked by the BSM 617. Also, a shift ofthe threshold voltage Vth of the LTPS thin film transistor 130 which mayoccur when the potential on the surface of the substrate 110 isincreased can also be suppressed by the BSM 617.

FIG. 7 is a schematic flowchart of a method of manufacturing an organiclight emitting display device including a multi-type thin filmtransistor according to an embodiment of the present disclosure. FIG. 8Athrough FIG. 8I are process cross-sectional views of a method ofmanufacturing an organic light emitting display device including amulti-type thin film transistor according to an embodiment of thepresent disclosure. FIG. 7 and FIG. 8A through FIG. 8I are a flowchartand process cross-sectional view of a method of manufacturing theorganic light emitting display device 100 illustrated in FIG. 1.Therefore, redundant description thereof will be omitted.

Firstly, the buffer layer 111 is formed on the substrate 110 (S1000).

Referring to FIG. 8A, the buffer layer 111 is deposited on the surfaceof the substrate 110. Specifically, the buffer layer 111 may be formedas a single layer by depositing any one of silicon nitride (SiNx) orsilicon oxide (SiOx) or as a multi-layer by alternately laminatingsilicon nitride (SiNx) and silicon oxide (SiOx). Otherwise, the bufferlayer 111 may be formed as a multi-layer by selecting any one of siliconnitride (SiNx) or silicon oxide (SiOx) with different properties such asa density or the like.

Then, the active layer 131 of the LTPS thin film transistor 130 and thefirst electrode 121 of the storage capacitor 120 are formed on thebuffer layer 111 (S1010).

Referring to FIG. 7 and FIG. 8A, an amorphous silicon (a-Si) layer 891is formed on a surface of the buffer layer 111 by depositing an a-Simaterial thereon (S1011) and a dehydrogenation process (S1012) isperformed to the a-Si layer 891. If a large amount of hydrogen ispresent in the a-Si layer 891, hydrogen in the a-Si layer 891 mayexplode during a crystallization process (S1013) as a subsequentprocess, which may cause a defect. Thus, the dehydrogenation processwhich is a process for removing hydrogen from the a-Si layer 891 isperformed after the a-Si layer 891 is formed and before thecrystallization process (S1013) is performed.

Then, after the dehydrogenation process (S1012) is completed, thecrystallization process (S1013) is performed to the a-Si layer 891. Thecrystallization process is a process for crystallizing amorphous silicon(a-Si) in the a-Si layer 891 into poly-silicon. For example, thecrystallization process may be performed through excimer laser annealing(ELA).

Then, referring to FIG. 7 and FIG. 8B, the crystallized a-Si layer 891is patterned to form the active layer 131 of the LTPS thin filmtransistor 130 and the first electrode 121 of the storage capacitor 120(S1014).

Then, the gate insulation layer 112 of the LTPS thin film transistor 130is formed (S1020), and the gate electrode 134 of the LTPS thin filmtransistor 130, the gate electrode 144 of the oxide semiconductor thinfilm transistor 140, and the second electrode 122 of the storagecapacitor 120 are formed (S1030).

Referring to FIG. 8C, the gate insulation layer 112 of the LTPS thinfilm transistor 130 is formed on the active layer 131 of the LTPS thinfilm transistor 130 and the first electrode 121 of the storage capacitor120. Specifically, the gate insulation layer 112 of the LTPS thin filmtransistor 130 may be formed as a single layer by depositing any one ofsilicon nitride (SiNx) or silicon oxide (SiOx) or as a multi-layer byalternately laminating silicon nitride (SiNx) and silicon oxide (SiOx).Otherwise, the gate insulation layer 112 may be formed as a multi-layerby selecting any one of silicon nitride (SiNx) or silicon oxide (SiOx)with different properties such as a density or the like.

Then, a gate electrode material is deposited on the gate insulationlayer 112 of the LTPS thin film transistor 130 and then patterned toform the gate electrode 134 of the LTPS thin film transistor 130, thegate electrode 144 of the oxide semiconductor thin film transistor 140,and the second electrode 122 of the storage capacitor 120. The gateelectrode material may include various metal materials such asmolybdenum (Mo).

Then, a doping process is performed to the active layer 131 of the LTPSthin film transistor 130 using the gate electrode 134 of the LTPS thinfilm transistor 130 as a mask (S1040).

Referring to FIG. 8D, impurities are injected to the active layer 131 ofthe LTPS thin film transistor 130 disposed under the gate electrode 134of the LTPS thin film transistor 130 using the gate electrode 134 of theLTPS thin film transistor 130 as a mask. Thus, the source area SA andthe drain area DA, i.e., a doping area, of the LTPS thin film transistor130 may be defined. The doping area may be defined in various waysdepending on a P-MOS thin film transistor, an N-MOS thin filmtransistor, or a C-MOS thin film transistor. For example, in case of theN-MOS thin film transistor, a high-density doping area may be formedfirst and then, a low-density doping area may be formed. Specifically,the high-density doping area may be defined using a photoresist having agreater size than the gate electrode 134 of the LTPS thin filmtransistor 130. Then, the photoresist may be removed and the low-densitydoping area (LDD) may be defined using the gate electrode 134 of theLTPS thin film transistor 130 as a mask.

In some embodiments, the doping area including the source area SA andthe drain area DA may be defined before the gate insulation layer 112 ofthe LTPS thin film transistor 130 is formed. That is, right after theactive layer 131 of the LTPS thin film transistor 130 and the firstelectrode 121 of the storage capacitor 120 are formed, the impuritiesmay also be doped using the photoresist. In this case, the firstelectrode 121 of the storage capacitor 120 may be doped with theimpurities.

Then, the interlayer insulation layer 150 of the LTPS thin filmtransistor 130 is formed on the gate electrode 134 of the LTPS thin filmtransistor 130, the gate electrode 144 of the oxide semiconductor thinfilm transistor 140, and the second electrode 122 of the storagecapacitor 120 (S1050).

Referring to FIG. 8E, the interlayer insulation layer 150 of the LTPSthin film transistor 130 may be formed on the gate electrode 134 of theLTPS thin film transistor 130, the gate electrode 144 of the oxidesemiconductor thin film transistor 140, and the second electrode 122 ofthe storage capacitor 120 by depositing silicon nitride (SiNx) thereon.The interlayer insulation layer 150 of the LTPS thin film transistor 130may be formed of an inorganic film having a high hydrogen content tosupply hydrogen to the active layer 131 of the LTPS thin film transistor130 during a subsequent hydrogenation process of the active layer 131 ofthe LTPS thin film transistor 130.

Then, an activation process is performed to the active layer 131 of theLTPS thin film transistor 130 (S1060), and a hydrogenation process isperformed to the active layer 131 of the LTPS thin film transistor 130(S1070).

As illustrated in FIG. 8E, after the interlayer insulation layer 150 isformed of silicon nitride (SiNx), the activation process is performed tothe active layer 131 of the LTPS thin film transistor 130 before thegate insulation layer 160 of the oxide semiconductor thin filmtransistor 140 is formed. After the activation process is performed, thehydrogenation process is performed to the active layer 131 of the LTPSthin film transistor 130. The hydrogenation process may be performedbefore and after the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 is formed.

Regarding the activation process to the active layer 131 of the LTPSthin film transistor 130, impurities (dopant) injected as a result ofthe doping process to the active layer 131 of the LTPS thin filmtransistor 130 are randomly present. Thus, the activation process to theactive layer 131 of the LTPS thin film transistor 130 is a process forpositioning the impurities in a silicon (Si) lattice. Further, thedoping process to the active layer 131 of the LTPS thin film transistor130 is a process of artificially injecting the impurities into theactive layer. Therefore, as a result of the doping process to the activelayer 131 of the LTPS thin film transistor 130, the silicon (Si) may bedamaged. Thus, the activation process may be performed to the activelayer 131 of the LTPS thin film transistor 130 to cure the damage to thesilicon (Si). For example, the activation process may be performed at atemperature of from about 480° C. to about 550° C. for about 120seconds.

Regarding the hydrogenation process to the active layer 131 of the LTPSthin film transistor 130, if poly-silicon has vacancies, the propertiesthereof deteriorate. Thus, the hydrogenation process to the active layer131 of the LTPS thin film transistor 130 is a process for filling thevacancies of the poly-silicon with hydrogen. The hydrogenation processto the active layer 131 of the LTPS thin film transistor 130 isperformed by diffusing hydrogen contained in the interlayer insulationlayer 150 of the LTPS thin film transistor 130 through a heat treatment.For example, the hydrogenation process may be performed at a temperatureof from about 350° C. to about 420° C. for about 3000 seconds. Thehydrogenation process to the active layer 131 of the LTPS thin filmtransistor 130 may stabilize the active layer 131 of the LTPS thin filmtransistor 130.

Then, the gate insulation layer 160 of the oxide semiconductor thin filmtransistor 140 is formed on the interlayer insulation layer 150 of theLTPS thin film transistor 130 (S1080). Then, the active layer 141 of theoxide semiconductor thin film transistor 140 is formed on the gateinsulation layer 160 of the oxide semiconductor thin film transistor 140(S1090). Otherwise, the hydrogenation process to the LTPS thin filmtransistor 130 may be performed after the interlayer insulation layer150 of the LTPS thin film transistor 130 is formed.

Referring to FIG. 8F, the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 may be formed on the interlayerinsulation layer 150 of the LTPS thin film transistor 130. The gateinsulation layer 160 of the oxide semiconductor thin film transistor 140may be formed of silicon oxide (SiOx) to suppress diffusion of hydrogenfrom the interlayer insulation layer 150 of the LTPS thin filmtransistor 130 into the active layer 141 of the oxide semiconductor thinfilm transistor 140.

Then, a metal oxide, e.g., indium-gallium-zinc oxide (hereinafter,referred to as “IGZO”), is deposited (S1091) on the gate insulationlayer 160 of the oxide semiconductor thin film transistor 140 to form anIGZO layer 892. FIG. 8F illustrates that the IGZO layer 892 is formedassuming that the active layer 141 of the oxide semiconductor thin filmtransistor 140 is formed of IGZO from among various metal oxides.However, the present disclosure is not limited thereto. Instead of IGZO,another metal oxide may also be used.

The deposition of IGZO is performed at a high temperature. Therefore,IGZO may be crystallized during the deposition of IGZO. If IGZO isdeposited at room temperature, IGZO may be in an amorphous state.However, if IGZO is deposited at a high temperature, indium (In),gallium (Ga), and zinc (Zn) have a layer structure and form a network.Further, as IGZO is crystallized at a high temperature, oxygen vacancieswithin the IGZO layer 892 are decreased. If there are a lot of oxygenvacancies within the IGZO layer 892, tunneling occurs, so that the IGZOlayer 892 may become conductive. Therefore, when IGZO is deposited,crystallization is performed at a high temperature. Accordingly, the BTSof the oxide semiconductor thin film transistor 140 can be improved andthe reliability can be increased.

Then, a heat treatment is performed to the IGZO layer 892 to stabilizethe IGZO layer 892 (S1092). Then, as illustrated in FIG. 8G, the IGZOlayer 892 is patterned (S1093) to form the active layer 141 of the oxidesemiconductor thin film transistor 140.

Then, as illustrated in FIG. 8H, contact holes are formed in the gateinsulation layer 112 and the interlayer insulation layer 150 of the LTPSthin film transistor 130 and the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 (S1100). Then, the sourceelectrode 132 and the drain electrode 133 of the LTPS thin filmtransistor 130 and the source electrode 142 and the drain electrode 143of the oxide semiconductor thin film transistor 140 are formed (S1110).

After the contact holes are formed in the gate insulation layer 112 andthe interlayer insulation layer 150 of the LTPS thin film transistor 130and the gate insulation layer 160 of the oxide semiconductor thin filmtransistor 140, the source electrode 132 and the drain electrode 133 ofthe LTPS thin film transistor 130 and the source electrode 142 and thedrain electrode 143 of the oxide semiconductor thin film transistor 140may be formed by depositing and patterning a source electrode materialand a drain electrode material on the gate insulation layer 160 and theactive layer of the oxide semiconductor thin film transistor 140. Thesource electrode 132 and the drain electrode 133 of the LTPS thin filmtransistor 130 and the source electrode 142 and the drain electrode 143of the oxide semiconductor thin film transistor 140 may be formed as athree-layer structure including titanium (Ti)/aluminum (Al)/titanium(Ti). In this case, a patterning process may be performed through dryetching.

In some embodiments, dry etching may be performed in two steps tosuppress damage to the active layer 141 of the oxide semiconductor thinfilm transistor 140. For example, primary dry etching may be performedat a high etching rate and secondary dry etching may be performed at alow etching rate. By performing the dry etching in two steps as such,damage to the active layer 141 of the oxide semiconductor thin filmtransistor 140 can be reduced.

Then, as illustrated in FIG. 8I, the passivation layer 170 is formed tocover the LTPS thin film transistor 130 and the oxide semiconductor thinfilm transistor 140 (S1120). The overcoating layer 113 is formed on thepassivation layer 170 (S1130) and the organic light emitting element 180is formed on the overcoating layer 113 (S1140). Then, the encapsulationunit 190 is formed on the organic light emitting element 180 (S1150).The passivation layer 170 may be formed as a double-layer structure asdescribed above.

FIG. 9 is a cross-sectional view of an organic light emitting displaydevice including a multi-type thin film transistor according to stillanother embodiment of the present disclosure. An organic light emittingdisplay device 900 illustrated in FIG. 9 is substantially the same asthe organic light emitting display device 100 illustrated in FIG. 1except that a gate electrode 944 of an oxide semiconductor thin filmtransistor 940 is changed in position, and an interlayer insulationlayer 950 of the LTPS thin film transistor 130 and a gate insulationlayer 960 of the oxide semiconductor thin film transistor 940 aremodified. Therefore, redundant description thereof will be omitted.

Referring to FIG. 9, the interlayer insulation layer 950 of the LTPSthin film transistor 130 is disposed on the gate electrode 134 of theLTPS thin film transistor 130. The interlayer insulation layer 950 maybe formed as a single layer or may be formed as two or more layershaving different properties from each other. For example, the interlayerinsulation layer 950 may be formed as a single layer of silicon nitride(SiNx) or a multi-layer including at least one layer formed of siliconnitride (SiNx).

The gate electrode 944 of the oxide semiconductor thin film transistor940 is disposed on the interlayer insulation layer 950 of the LTPS thinfilm transistor 130. The gate electrode 944 of the oxide semiconductorthin film transistor 940 is formed of a metal material. For example, thegate electrode 944 may be formed of the same material as the gateelectrode 134 of the LTPS thin film transistor 130.

The gate insulation layer 960 of the oxide semiconductor thin filmtransistor 940 formed of silicon oxide (SiOx) is disposed on the gateelectrode 944 of the oxide semiconductor thin film transistor 940.Further, the active layer 141 of the oxide semiconductor thin filmtransistor 940 is disposed on the gate insulation layer 960 of the oxidesemiconductor thin film transistor 940.

In the organic light emitting display device 900 according to stillanother exemplary embodiment of the present disclosure, only the gateinsulation layer 960 formed as a single layer is disposed between theactive layer 141 and the gate electrode 944 of the oxide semiconductorthin film transistor 940. That is, in the organic light emitting displaydevice 900 according to still another embodiment of the presentdisclosure, the gate insulation layer 960 of the oxide semiconductorthin film transistor 940 can be tuned independently. Thus, theproperties of the oxide semiconductor thin film transistor 940 can beindividually controlled regardless of the other components. Morespecifically, an on-current of the oxide semiconductor thin filmtransistor 940 is affected by a distance between the active layer 141and the gate electrode of the oxide semiconductor thin film transistor940. Meanwhile, if any layer other than the gate insulation layer 960 ofthe oxide semiconductor thin film transistor 940 is additionallydisposed between the active layer 141 and the gate electrode of theoxide semiconductor thin film transistor 940, there may be a change inthe on-current of the oxide semiconductor thin film transistor 940. Inthis case, there is a limit to the control of distance between theactive layer 141 and the gate electrode of the oxide semiconductor thinfilm transistor 940 to improve only the on-current of the oxidesemiconductor thin film transistor 940. However, in the organic lightemitting display device 900 according to still another embodiment of thepresent disclosure, only the gate insulation layer 960 is disposedbetween the active layer 141 and the gate electrode of the oxidesemiconductor thin film transistor 940. Therefore, it is possible toindependently control the distance between the active layer 141 and thegate electrode of the oxide semiconductor thin film transistor 940 andthus possible to reduce the distance between the active layer 141 andthe gate electrode of the oxide semiconductor thin film transistor 940.Therefore, the on-current of the oxide semiconductor thin filmtransistor 940 can be improved. Further, since the gate insulation layer960 of the oxide semiconductor thin film transistor 940 is separatelyused, the degree of freedom in design can also be increased.

In the organic light emitting display device 900 illustrated in FIG. 9,the storage capacitor 120 includes the first electrode 121 and thesecond electrode 122, but is not limited thereto. The storage capacitor120 may further include a third electrode or a fourth electrode. Forexample, a third electrode of the storage capacitor 120 may be disposedon the interlayer insulation layer 950 of the LTPS thin film transistor130. In this case, the third electrode may be formed of the samematerial through the same process as the gate electrode 944 of the oxidesemiconductor thin film transistor 940. Further, a fourth electrode ofthe storage capacitor 120 may be disposed on the gate insulation layer960 of the oxide semiconductor thin film transistor 940. In this case,the fourth electrode may be formed of the same material through the sameprocess as the source electrode 142 and the drain electrode 143 of theoxide semiconductor thin film transistor 940. As such, since the thirdelectrode or the fourth electrode of the storage capacitor 120 isfurther disposed, a capacitance value of the storage capacitor 120 canbe increased. Further, the storage capacitor 120 can be formed during amanufacturing process of the LTPS thin film transistor 130 or the oxidesemiconductor thin film transistor 940 without any additional processes,which is efficient in terms of the processing costs and the processingtime.

Further, the structures of the above-described organic light emittingdisplay devices 100, 400, 500, 600B, and 600C can be applied to theorganic light emitting display device 900 illustrated in FIG. 9. Forexample, the plurality of overcoating layers 513 and 515 and theadditional metal layers 519, 524, and 523 of the organic light emittingdisplay device 500 illustrated in FIG. 5 can be applied to the organiclight emitting display device 900. Otherwise, the BSM 617 of the organiclight emitting display devices 600B and 600C illustrated in FIG. 6B andFIG. 6C can also be applied thereto.

FIG. 7 illustrates that in the method of manufacturing an organic lightemitting display device including a multi-type thin film transistoraccording to an embodiment of the present disclosure, the activationprocess and the hydrogenation process to the active layer 131 of theLTPS thin film transistor 130 and the heat treatment to the active layer141 of the oxide semiconductor thin film transistor 140 are separatelyperformed. However, the activation process and the hydrogenation processto the active layer 131 of the LTPS thin film transistor 130 and theheat treatment to the active layer 141 of the oxide semiconductor thinfilm transistor 140 may be performed at the same process. That is, bycontrolling a processing temperature in the heat treatment to the activelayer 141 of the oxide semiconductor thin film transistor 140, theactivation process and the hydrogenation process to the active layer 131of the LTPS thin film transistor 130 may be performed together with theheat treatment to the active layer 141 of the oxide semiconductor thinfilm transistor 140. If the processes are performed as such, an effectof hydrogen on the active layer 141 of the oxide semiconductor thin filmtransistor 140 may be increased, but a plurality of processes can beintegrated into a single process. Thus, the manufacturing process can bemore simplified.

As described above, if the activation process and the hydrogenationprocess to the active layer 131 of the LTPS thin film transistor 130 andthe heat treatment to the active layer 141 of the oxide semiconductorthin film transistor 140 are separately performed, the activationprocess and the hydrogenation process to the active layer 131 of theLTPS thin film transistor 130 need to be performed before the activelayer 141 of the oxide semiconductor thin film transistor 140 is formed.In this case, after the interlayer insulation layer 150 of the LTPS thinfilm transistor 130 is formed and only the activation process isperformed to the active layer 131 of the LTPS thin film transistor 130,the gate insulation layer 160 of the oxide semiconductor thin filmtransistor 140 may be formed. Then, the hydrogenation process may beperformed to the active layer 131 of the LTPS thin film transistor 130(Example 1). Otherwise, after the interlayer insulation layer 150 of theLTPS thin film transistor 130 is formed and all of the activationprocess and the hydrogenation process are performed to the active layer131 of the LTPS thin film transistor 130, the gate insulation layer 160of the oxide semiconductor thin film transistor 140 may be formed(Example 2). Alternatively, after all of the interlayer insulation layer150 of the LTPS thin film transistor 130 and the gate insulation layer160 of the oxide semiconductor thin film transistor 140 are formed, theactivation process and the hydrogenation process may be performed to theactive layer 131 of the LTPS thin film transistor 130 (ComparativeExample). In the method of manufacturing an organic light emittingdisplay device according to an embodiment of the present disclosure, theactivation process is performed to the active layer 131 of the LTPS thinfilm transistor 130 before the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 is formed. Thus, an effect ofhydrogen on the active layer 141 of the oxide semiconductor thin filmtransistor 140 can be minimized. A more detailed explanation will beprovided with reference to FIG. 10A through FIG. 10C and FIG. 11.

FIG. 10A is a schematic flowchart of an activation process and ahydrogenation process of an LTPS thin film transistor in a method ofmanufacturing an organic light emitting display device including amulti-type thin film transistor according to Comparative Example. FIG.10B and FIG. 10C are schematic flowcharts of an activation process and ahydrogenation process of an LTPS thin film transistor in a method ofmanufacturing an organic light emitting display device including amulti-type thin film transistor according to an embodiment and anotherembodiment of the present disclosure. FIG. 11 is a table provided toexplain Vth MAP and Vth variation caused by an activation process and ahydrogenation process of an LTPS thin film transistor in a method ofmanufacturing an organic light emitting display device including amulti-type thin film transistor according to an embodiment of thepresent disclosure and Comparative Example.

FIG. 10A is a flowchart of Comparative Example described above. FIG. 10Bis a flowchart of Example 1 described above. FIG. 10C is a flowchart ofExample 2 of the present disclosure. FIG. 11 shows Vth MAPs and Vthvariation ranges of samples of Comparative Example, Example 1, andExample 2 after organic light emitting display devices each including amulti-type thin film transistor are manufactured by the processesaccording to Comparative Example, Example 1, and Example 2 illustratedin FIG. 10A through FIG. 10C, respectively. Herein, the Vth MAP is adiagram showing a difference in threshold voltage Vth in an active layerof an oxide semiconductor thin film transistor. In a specific area ofthe Vth Map, a threshold voltage Vth is low at a high hatching density,i.e., point density. Further, the Vth variation range shows the highestthreshold voltage (Vth) value and the lowest threshold voltage (Vth)value in the Vth MAP. In each of Comparative Example, Example 1, andExample 2, an oxide semiconductor thin film transistor was manufacturedsuch that a channel area of the oxide semiconductor thin film transistorhas a width of 6 μm and a length of 6 μm. In this case, the samples are20 oxide semiconductor thin film transistors formed on a single mothersubstrate.

Referring to FIG. 10A, in Comparative Example, the interlayer insulationlayer 150 of the LTPS thin film transistor 130 is formed (S1050), thegate insulation layer 160 of the oxide semiconductor thin filmtransistor 140 is formed (S1080′), and an activation process (S1060′)and a hydrogenation process (S1070′) are performed to the active layer131 of the LTPS thin film transistor 130. That is, in a state where thegate insulation layer 160 of the oxide semiconductor thin filmtransistor 140 formed of silicon oxide (SiOx) is disposed on theinterlayer insulation layer 150 of the LTPS thin film transistor 130formed of silicon nitride (SiNx), the activation process and thehydrogenation process are performed in series to the active layer 131 ofthe LTPS thin film transistor 130. Thus, while the activation processand the hydrogenation process are performed to the active layer 131 ofthe LTPS thin film transistor 130, hydrogen contained in the interlayerinsulation layer 150 of the LTPS thin film transistor 130 is diffusedinto the gate insulation layer 160 of the oxide semiconductor thin filmtransistor 140. Thus, a large amount of hydrogen is included in the gateinsulation layer 160 of the oxide semiconductor thin film transistor140. Therefore, while the active layer 141 of the oxide semiconductorthin film transistor 140 is formed later and a heat treatment isperformed to the active layer 141 of the oxide semiconductor thin filmtransistor 140, the large amount of hydrogen contained in the gateinsulation layer 160 of the oxide semiconductor thin film transistor 140may be diffused into the active layer 141 of the oxide semiconductorthin film transistor 140. Thus, the threshold voltage Vth of the oxidesemiconductor thin film transistor 140 may be changed. Therefore,referring to FIG. 11, the Vth variation in the Comparative Example is ashigh as 4.2 V.

Referring to FIG. 10B, in Example 1, the interlayer insulation layer 150of the LTPS thin film transistor 130 is formed (S1050), an activationprocess is performed to the active layer 131 of the LTPS thin filmtransistor 130 (S1060), the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 is formed (S1080′), and ahydrogenation process is performed to the active layer 131 of the LTPSthin film transistor 130 (S1070′). That is, in a state where theinterlayer insulation layer 150 of the LTPS thin film transistor 130formed of silicon nitride (SiNx) is disposed, the activation process isperformed to the active layer 131 of the LTPS thin film transistor 130.Then, in a state where the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 formed of silicon oxide (SiOx) isdisposed, the hydrogenation process is performed to the active layer 131of the LTPS thin film transistor 130. Thus, during the activationprocess to the active layer 131 of the LTPS thin film transistor 130,the gate insulation layer 160 of the oxide semiconductor thin filmtransistor 140 is not present on the interlayer insulation layer 150 ofthe LTPS thin film transistor 130. Therefore, hydrogen is not diffusedfrom the interlayer insulation layer 150 of the LTPS thin filmtransistor 130 into an upper layer. However, in a state where the gateinsulation layer 160 of the oxide semiconductor thin film transistor 140is disposed, the hydrogenation process is performed to the active layer131 of the LTPS thin film transistor 130. Thus, during the hydrogenationprocess to the active layer 131 of the LTPS thin film transistor 130,hydrogen may be diffused from the interlayer insulation layer 150 of theLTPS thin film transistor 130 into the gate insulation layer 160 of theoxide semiconductor thin film transistor 140. However, the activationprocess performed at a higher processing temperature than thehydrogenation process may be performed before the gate insulation layer160 of the oxide semiconductor thin film transistor 140 is formed, sothat diffusion of hydrogen into the gate insulation layer 160 of theoxide semiconductor thin film transistor 140 can be minimized. Further,as described above, referring to FIG. 8B, the gate insulation layer 160of the oxide semiconductor thin film transistor 140 may be formed as amulti-layer with a difference in density. For example, the gateinsulation layer 160 of the oxide semiconductor thin film transistor 140may include a first gate insulation layer 861 and a second gateinsulation layer 862 formed of silicon oxide (SiOx). In this case, afilm density of the second gate insulation layer 862 disposed in contactwith the active layer 141 of the oxide semiconductor thin filmtransistor 140 may be higher than that of the first gate insulationlayer 861. Therefore, while the active layer 141 of the oxidesemiconductor thin film transistor 140 is formed later and a heattreatment is performed, the second gate insulation layer 862 having ahigher film density can minimize diffusion of hydrogen into the activelayer 141 of the oxide semiconductor thin film transistor 140. Referringto FIG. 11, it can be seen that the Vth variation of Example 1 is muchlower than that of Comparative Example.

Referring to FIG. 10C, in Example 2, the interlayer insulation layer 150of the LTPS thin film transistor 130 is formed (S1050), an activationprocess (S1060) and a hydrogenation process (S1070) are performed to theactive layer 131 of the LTPS thin film transistor 130, and the gateinsulation layer 160 of the oxide semiconductor thin film transistor 140is formed (S1080). That is, in a state where the interlayer insulationlayer 150 of the LTPS thin film transistor 130 formed of silicon nitride(SiNx) is disposed, all of the activation process and the hydrogenationprocess are performed to the active layer 131 of the LTPS thin filmtransistor 130. Then, the gate insulation layer 160 of the oxidesemiconductor thin film transistor 140 formed of silicon oxide (SiOx) isdisposed. Thus, during the activation process and the hydrogenationprocess to the active layer 131 of the LTPS thin film transistor 130,any layer is not present on the interlayer insulation layer 150 of theLTPS thin film transistor 130. Therefore, hydrogen is not diffused fromthe interlayer insulation layer 150 of the LTPS thin film transistor 130into an upper layer. Further, during the activation process and thehydrogenation process to the active layer 131 of the LTPS thin filmtransistor 130, hydrogen contained in a surface of the interlayerinsulation layer 150 of the LTPS thin film transistor 130 in contactwith the gate insulation layer 160 of the oxide semiconductor thin filmtransistor 140 may be removed. Therefore, hydrogen is not diffused fromthe interlayer insulation layer 150 of the LTPS thin film transistor 130into the gate insulation layer 160 of the oxide semiconductor thin filmtransistor 140 formed later. Therefore, while the active layer 141 ofthe oxide semiconductor thin film transistor 140 is formed later and aheat treatment is performed, the amount of hydrogen diffused from thegate insulation layer 160 of the oxide semiconductor thin filmtransistor 140 and the interlayer insulation layer 150 of the LTPS thinfilm transistor 130 is remarkably reduced. Referring to FIG. 11, it canbe seen that the Vth variation of Example 2 is much lower than that ofComparative Example.

Although the exemplary embodiments of the present disclosure have beendescribed in detail with reference to the accompanying drawings, thepresent disclosure is not limited thereto and may be embodied in manydifferent forms without departing from the technical concept of thepresent disclosure. Therefore, the exemplary embodiments of the presentdisclosure are provided for illustrative purposes only but not intendedto limit the technical concept of the present disclosure. The scope ofthe technical concept of the present disclosure is not limited thereto.The protective scope of the present disclosure should be construed basedon the following claims, and all the technical concepts in theequivalent scope thereof should be construed as falling within the scopeof the present disclosure.

What is claimed is:
 1. A method of manufacturing an organic lightemitting display device in which a low temperature poly-silicon (LTPS)thin film transistor and an oxide semiconductor thin film transistor areformed on a substrate, comprising: a first step of forming an interlayerinsulation layer of the LTPS thin film transistor on the substrate; asecond step of forming a gate insulation layer of the oxidesemiconductor thin film transistor on the interlayer insulation layer ofthe LTPS thin film transistor; and an activation process for curing anactive layer of the LTPS thin film transistor, wherein the activationprocess is performed between the first step and the second step, andwherein a threshold voltage variation of the oxide semiconductor thinfilm transistor is reduced as compared with a case where the activationprocess is performed after the second step.
 2. The method ofmanufacturing the organic light emitting display device according toclaim 1, further comprising: a hydrogenation process for fillingvacancies within the active layer of the LTPS thin film transistor withhydrogen atoms, wherein the hydrogenation process is performed after theactivation process is completed.
 3. The method of manufacturing theorganic light emitting display device according to claim 2, wherein thehydrogenation process is performed after the second step is completed,and wherein the threshold voltage variation of the oxide semiconductorthin film transistor is reduced as compared with a case where theactivation process and the hydrogenation process are performed after thesecond step.
 4. The method of manufacturing the organic light emittingdisplay device according to claim 3, further comprising: forming anactive layer of the oxide semiconductor thin film transistor on the gateinsulation layer of the oxide semiconductor thin film transistor; andperforming a heat treatment to the active layer of the oxidesemiconductor thin film transistor after the second step is completed,wherein performing the heat treatment is at least partially overlappedwith the hydrogenation process.
 5. The method of manufacturing theorganic light emitting display device according to claim 2, wherein aprocessing temperature of the activation process is higher than that ofthe hydrogenation process and a processing time of the activationprocess is shorter than that of the hydrogenation process.
 6. A methodof manufacturing an organic light emitting display device, comprising:forming a first active layer of an LTPS thin film transistor on asubstrate; forming a hydrogen layer on the first active layer;performing an activation process for curing the first active layer;performing a hydrogenation process for supplying hydrogen to the firstactive layer after the activation process; forming a hydrogen resistantlayer on the hydrogen layer; and forming a second active layer of theoxide semiconductor thin film transistor on the hydrogen resistantlayer, wherein the activation process and the hydrogenation process arecompleted before the forming of the hydrogen resistant layer in order tominimize exposure of the second active layer to hydrogen.
 7. The methodof manufacturing the organic light emitting display device according toclaim 6, wherein during the hydrogenation process, at least a part ofhydrogen in the hydrogen layer is moved into the first active layer andat least a part of hydrogen on a surface of the hydrogen layer incontact with the hydrogen resistant layer is removed.
 8. The method ofmanufacturing the organic light emitting display device according toclaim 6, further comprising: forming a gate insulation layer betweenforming the first active layer and forming the hydrogen layer; andforming a first gate electrode of the LTPS thin film transistor betweenforming the gate insulation layer and forming the hydrogen layer.
 9. Themethod of manufacturing the organic light emitting display deviceaccording to claim 8, further comprising: performing a doping process tothe first active layer after the forming of the first gate electrode.10. The method of manufacturing the organic light emitting displaydevice according to claim 9, wherein the activation process is performedafter the doping process and the forming of the hydrogen layer arefinished.
 11. The method of manufacturing the organic light emittingdisplay device according to claim 8, further comprising: forming asecond gate electrode of the oxide semiconductor thin film transistor,wherein the second gate electrode is formed directly on the gateinsulation layer or the hydrogen layer.
 12. The method of manufacturingthe organic light emitting display device according to claim 11, whereinthe second gate electrode is formed of the same material as the firstgate electrode.
 13. The method of manufacturing the organic lightemitting display device according to claim 11, further comprising:forming a first source electrode and a first drain electrode of the LTPSthin film transistor on the hydrogen blocking layer; and forming asecond source electrode and a second drain electrode of the oxidesemiconductor thin film transistor on the hydrogen blocking layer. 14.The method of manufacturing the organic light emitting display deviceaccording to claim 13, wherein the first source electrode, the secondsource electrode, the first drain electrode, and the second drainelectrode are formed of the same material through the same process. 15.The method of manufacturing the organic light emitting display deviceaccording to claim 13, further comprising: forming a plurality ofcontact holes in the gate insulation layer, the hydrogen layer, and thehydrogen resistant layer, respectively, wherein the first sourceelectrode and the first drain electrode are electrically connected tothe first active layer through the plurality of contact holes.
 16. Themethod of manufacturing the organic light emitting display deviceaccording to claim 6, wherein forming the hydrogen resistant layerincludes forming a first hydrogen resistant layer, and forming a secondhydrogen resistant layer on the first hydrogen resistant layer.
 17. Themethod of manufacturing the organic light emitting display deviceaccording to claim 16, wherein the first hydrogen resistant layer andthe second hydrogen resistant layer include the same material, and adensity of the first hydrogen resistant layer is different from that ofthe second hydrogen resistant layer.
 18. The method of manufacturing theorganic light emitting display device according to claim 17, whereineach of the first hydrogen resistant layer and the second hydrogenresistant layer includes silicon oxide (SiOx).
 19. The method ofmanufacturing the organic light emitting display device according toclaim 16, wherein the second hydrogen resistant layer is formed directlyon the second active layer.
 20. The method of manufacturing the organiclight emitting display device according to claim 16, wherein the secondhydrogen resistant layer is formed to have a higher density than thefirst hydrogen resistant layer.